diff --git a/Cargo.lock b/Cargo.lock
index aed11d0845e8b4..6a758ce09b2e00 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -456,7 +456,7 @@ dependencies = [
  "bitflags 2.5.0",
  "cexpr",
  "clang-sys",
- "itertools",
+ "itertools 0.10.5",
  "lazy_static",
  "lazycell",
  "log",
@@ -1186,6 +1186,7 @@ dependencies = [
  "libz-sys",
  "log",
  "lsp-types",
+ "malva",
  "memmem",
  "monch",
  "napi_sym",
@@ -1612,7 +1613,7 @@ dependencies = [
  "hyper 0.14.28",
  "hyper 1.4.1",
  "hyper-util",
- "itertools",
+ "itertools 0.10.5",
  "memmem",
  "mime",
  "once_cell",
@@ -3852,6 +3853,15 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.11"
@@ -4235,6 +4245,19 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "malva"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf982faadf37679302c3fcd8d843d29bf4bb4d323323cffb2f5217ad39578470"
+dependencies = [
+ "aho-corasick",
+ "itertools 0.13.0",
+ "memchr",
+ "raffia",
+ "tiny_pretty",
+]
+
 [[package]]
 name = "maplit"
 version = "1.0.2"
@@ -5290,7 +5313,7 @@ checksum = "119533552c9a7ffacc21e099c24a0ac8bb19c2a2a3f363de84cd9b844feab270"
 dependencies = [
  "bytes",
  "heck 0.4.1",
- "itertools",
+ "itertools 0.10.5",
  "lazy_static",
  "log",
  "multimap",
@@ -5311,7 +5334,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e5d2d8d10f3c6ded6da8b05b5fb3b8a5082514344d56c9f871412d29b4e075b4"
 dependencies = [
  "anyhow",
- "itertools",
+ "itertools 0.10.5",
  "proc-macro2",
  "quote",
  "syn 1.0.109",
@@ -5473,6 +5496,27 @@ dependencies = [
  "nibble_vec",
 ]
 
+[[package]]
+name = "raffia"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a26ea01d105c934a90ddd1fca6a343bec14e1a24b72126ee6f364f5a5dd5ec2"
+dependencies = [
+ "raffia_macro",
+ "smallvec",
+]
+
+[[package]]
+name = "raffia_macro"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4fdb50eb5bf734fa5a770680a61876a6ec77b99c1e0e52d1f18ad6ebfa85759f"
+dependencies = [
+ "heck 0.5.0",
+ "quote",
+ "syn 2.0.72",
+]
+
 [[package]]
 name = "rand"
 version = "0.8.5"
diff --git a/cli/Cargo.toml b/cli/Cargo.toml
index 0ea7d95ee41bf9..df7323e71e58b7 100644
--- a/cli/Cargo.toml
+++ b/cli/Cargo.toml
@@ -123,6 +123,7 @@ libc.workspace = true
 libz-sys.workspace = true
 log = { workspace = true, features = ["serde"] }
 lsp-types.workspace = true
+malva = "=0.8.0"
 memmem.workspace = true
 monch.workspace = true
 notify.workspace = true
diff --git a/cli/args/flags.rs b/cli/args/flags.rs
index e28ce549b45d1a..acdcaf8a711d04 100644
--- a/cli/args/flags.rs
+++ b/cli/args/flags.rs
@@ -200,6 +200,7 @@ pub struct FmtFlags {
   pub prose_wrap: Option<String>,
   pub no_semicolons: Option<bool>,
   pub watch: Option<WatchFlags>,
+  pub unstable_css: bool,
   pub unstable_yaml: bool,
 }
 
@@ -2018,8 +2019,8 @@ Ignore formatting a file by adding an ignore comment at the top of the file:
             // prefer using ts for formatting instead of js because ts works in more scenarios
             .default_value("ts")
             .value_parser([
-              "ts", "tsx", "js", "jsx", "md", "json", "jsonc", "yml", "yaml",
-              "ipynb",
+              "ts", "tsx", "js", "jsx", "md", "json", "jsonc", "css", "scss",
+              "sass", "less", "yml", "yaml", "ipynb",
             ]),
         )
         .arg(
@@ -2096,6 +2097,13 @@ Ignore formatting a file by adding an ignore comment at the top of the file:
               "Don't use semicolons except where necessary. Defaults to false.",
             ),
         )
+        .arg(
+          Arg::new("unstable-css")
+            .long("unstable-css")
+            .help("Enable formatting CSS, SCSS, Sass and Less files.")
+            .value_parser(FalseyValueParser::new())
+            .action(ArgAction::SetTrue),
+        )
         .arg(
           Arg::new("unstable-yaml")
             .long("unstable-yaml")
@@ -4163,6 +4171,7 @@ fn fmt_parse(flags: &mut Flags, matches: &mut ArgMatches) {
   let single_quote = matches.remove_one::<bool>("single-quote");
   let prose_wrap = matches.remove_one::<String>("prose-wrap");
   let no_semicolons = matches.remove_one::<bool>("no-semicolons");
+  let unstable_css = matches.get_flag("unstable-css");
   let unstable_yaml = matches.get_flag("unstable-yaml");
 
   flags.subcommand = DenoSubcommand::Fmt(FmtFlags {
@@ -4175,6 +4184,7 @@ fn fmt_parse(flags: &mut Flags, matches: &mut ArgMatches) {
     prose_wrap,
     no_semicolons,
     watch: watch_arg_parse(matches),
+    unstable_css,
     unstable_yaml,
   });
 }
@@ -5881,6 +5891,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -5905,6 +5916,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -5929,6 +5941,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -5953,6 +5966,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Some(Default::default()),
         }),
@@ -5966,6 +5980,7 @@ mod tests {
       "fmt",
       "--watch",
       "--no-clear-screen",
+      "--unstable-css",
       "--unstable-yaml"
     ]);
     assert_eq!(
@@ -5983,6 +5998,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: true,
           unstable_yaml: true,
           watch: Some(WatchFlags {
             hmr: false,
@@ -6018,6 +6034,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Some(Default::default()),
         }),
@@ -6042,6 +6059,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -6074,6 +6092,7 @@ mod tests {
           single_quote: None,
           prose_wrap: None,
           no_semicolons: None,
+          unstable_css: false,
           unstable_yaml: false,
           watch: Some(Default::default()),
         }),
@@ -6111,6 +6130,7 @@ mod tests {
           single_quote: Some(true),
           prose_wrap: Some("never".to_string()),
           no_semicolons: Some(true),
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
@@ -6142,6 +6162,7 @@ mod tests {
           single_quote: Some(false),
           prose_wrap: None,
           no_semicolons: Some(false),
+          unstable_css: false,
           unstable_yaml: false,
           watch: Default::default(),
         }),
diff --git a/cli/args/mod.rs b/cli/args/mod.rs
index bd49c0c1519da5..afad0528c3e2f5 100644
--- a/cli/args/mod.rs
+++ b/cli/args/mod.rs
@@ -281,6 +281,7 @@ impl BenchOptions {
 
 #[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
 pub struct UnstableFmtOptions {
+  pub css: bool,
   pub yaml: bool,
 }
 
@@ -314,6 +315,7 @@ impl FmtOptions {
     Self {
       options: resolve_fmt_options(fmt_flags, fmt_config.options),
       unstable: UnstableFmtOptions {
+        css: unstable.css || fmt_flags.unstable_css,
         yaml: unstable.yaml || fmt_flags.unstable_yaml,
       },
       files: fmt_config.files,
@@ -1330,8 +1332,10 @@ impl CliOptions {
   }
 
   pub fn resolve_config_unstable_fmt_options(&self) -> UnstableFmtOptions {
+    let workspace = self.workspace();
     UnstableFmtOptions {
-      yaml: self.workspace().has_unstable("fmt-yaml"),
+      css: workspace.has_unstable("fmt-css"),
+      yaml: workspace.has_unstable("fmt-yaml"),
     }
   }
 
@@ -1664,6 +1668,7 @@ impl CliOptions {
         "sloppy-imports",
         "byonm",
         "bare-node-builtins",
+        "fmt-css",
         "fmt-yaml",
       ]);
       // add more unstable flags to the same vector holding granular flags
diff --git a/cli/lsp/language_server.rs b/cli/lsp/language_server.rs
index 314c9ec14773a5..186c941985e45f 100644
--- a/cli/lsp/language_server.rs
+++ b/cli/lsp/language_server.rs
@@ -1368,6 +1368,9 @@ impl Inner {
         .data_for_specifier(&specifier)
         .map(|d| &d.member_dir.workspace);
       let unstable_options = UnstableFmtOptions {
+        css: maybe_workspace
+          .map(|w| w.has_unstable("fmt-css"))
+          .unwrap_or(false),
         yaml: maybe_workspace
           .map(|w| w.has_unstable("fmt-yaml"))
           .unwrap_or(false),
diff --git a/cli/tools/fmt.rs b/cli/tools/fmt.rs
index c4eebddf7a43c7..348e2d862a10bf 100644
--- a/cli/tools/fmt.rs
+++ b/cli/tools/fmt.rs
@@ -244,6 +244,10 @@ fn format_markdown(
           | "typescript"
           | "json"
           | "jsonc"
+          | "css"
+          | "scss"
+          | "sass"
+          | "less"
           | "yml"
           | "yaml"
       ) {
@@ -263,6 +267,13 @@ fn format_markdown(
             json_config.line_width = line_width;
             dprint_plugin_json::format_text(&fake_filename, text, &json_config)
           }
+          "css" | "scss" | "sass" | "less" => {
+            if unstable_options.css {
+              format_css(&fake_filename, text, fmt_options)
+            } else {
+              Ok(None)
+            }
+          }
           "yml" | "yaml" => {
             if unstable_options.yaml {
               pretty_yaml::format_text(
@@ -305,6 +316,20 @@ pub fn format_json(
   dprint_plugin_json::format_text(file_path, file_text, &config)
 }
 
+pub fn format_css(
+  file_path: &Path,
+  file_text: &str,
+  fmt_options: &FmtOptionsConfig,
+) -> Result<Option<String>, AnyError> {
+  malva::format_text(
+    file_text,
+    malva::detect_syntax(file_path).unwrap_or(malva::Syntax::Css),
+    &get_resolved_malva_config(fmt_options),
+  )
+  .map(Some)
+  .map_err(AnyError::from)
+}
+
 /// Formats a single TS, TSX, JS, JSX, JSONC, JSON, MD, or IPYNB file.
 pub fn format_file(
   file_path: &Path,
@@ -319,6 +344,13 @@ pub fn format_file(
       format_markdown(file_text, fmt_options, unstable_options)
     }
     "json" | "jsonc" => format_json(file_path, file_text, fmt_options),
+    "css" | "scss" | "sass" | "less" => {
+      if unstable_options.css {
+        format_css(file_path, file_text, fmt_options)
+      } else {
+        Ok(None)
+      }
+    }
     "yml" | "yaml" => {
       if unstable_options.yaml {
         pretty_yaml::format_text(
@@ -737,6 +769,58 @@ fn get_resolved_json_config(
   builder.build()
 }
 
+fn get_resolved_malva_config(
+  options: &FmtOptionsConfig,
+) -> malva::config::FormatOptions {
+  use malva::config::*;
+
+  let layout_options = LayoutOptions {
+    print_width: options.line_width.unwrap_or(80) as usize,
+    use_tabs: options.use_tabs.unwrap_or_default(),
+    indent_width: options.indent_width.unwrap_or(2) as usize,
+    line_break: LineBreak::Lf,
+  };
+
+  let language_options = LanguageOptions {
+    hex_case: HexCase::Lower,
+    hex_color_length: None,
+    quotes: if let Some(true) = options.single_quote {
+      Quotes::PreferSingle
+    } else {
+      Quotes::PreferDouble
+    },
+    operator_linebreak: OperatorLineBreak::Before,
+    block_selector_linebreak: BlockSelectorLineBreak::Consistent,
+    omit_number_leading_zero: false,
+    trailing_comma: true,
+    format_comments: false,
+    linebreak_in_pseudo_parens: true,
+    declaration_order: None,
+    single_line_block_threshold: None,
+    keyframe_selector_notation: None,
+    attr_value_quotes: AttrValueQuotes::Always,
+    prefer_single_line: false,
+    selectors_prefer_single_line: None,
+    function_args_prefer_single_line: None,
+    sass_content_at_rule_prefer_single_line: None,
+    sass_include_at_rule_prefer_single_line: None,
+    sass_map_prefer_single_line: None,
+    sass_module_config_prefer_single_line: None,
+    sass_params_prefer_single_line: None,
+    less_import_options_prefer_single_line: None,
+    less_mixin_args_prefer_single_line: None,
+    less_mixin_params_prefer_single_line: None,
+    top_level_declarations_prefer_single_line: None,
+    selector_override_comment_directive: "deno-fmt-selector-override".into(),
+    ignore_comment_directive: "deno-fmt-ignore".into(),
+  };
+
+  FormatOptions {
+    layout: layout_options,
+    language: language_options,
+  }
+}
+
 fn get_resolved_yaml_config(
   options: &FmtOptionsConfig,
 ) -> pretty_yaml::config::FormatOptions {
@@ -864,6 +948,10 @@ fn is_supported_ext_fmt(path: &Path) -> bool {
         | "mts"
         | "json"
         | "jsonc"
+        | "css"
+        | "scss"
+        | "sass"
+        | "less"
         | "md"
         | "mkd"
         | "mkdn"
@@ -906,6 +994,14 @@ mod test {
     assert!(is_supported_ext_fmt(Path::new("foo.JSONC")));
     assert!(is_supported_ext_fmt(Path::new("foo.json")));
     assert!(is_supported_ext_fmt(Path::new("foo.JsON")));
+    assert!(is_supported_ext_fmt(Path::new("foo.css")));
+    assert!(is_supported_ext_fmt(Path::new("foo.Css")));
+    assert!(is_supported_ext_fmt(Path::new("foo.scss")));
+    assert!(is_supported_ext_fmt(Path::new("foo.SCSS")));
+    assert!(is_supported_ext_fmt(Path::new("foo.sass")));
+    assert!(is_supported_ext_fmt(Path::new("foo.Sass")));
+    assert!(is_supported_ext_fmt(Path::new("foo.less")));
+    assert!(is_supported_ext_fmt(Path::new("foo.LeSS")));
     assert!(is_supported_ext_fmt(Path::new("foo.yml")));
     assert!(is_supported_ext_fmt(Path::new("foo.Yml")));
     assert!(is_supported_ext_fmt(Path::new("foo.yaml")));
diff --git a/tests/integration/fmt_tests.rs b/tests/integration/fmt_tests.rs
index dab2b2ce45c8b5..7a37ec2fce792d 100644
--- a/tests/integration/fmt_tests.rs
+++ b/tests/integration/fmt_tests.rs
@@ -31,6 +31,12 @@ fn fmt_test() {
   let badly_formatted_json = t.path().join("badly_formatted.json");
   badly_formatted_original_json.copy(&badly_formatted_json);
 
+  let fixed_css = testdata_fmt_dir.join("badly_formatted_fixed.css");
+  let badly_formatted_original_css =
+    testdata_fmt_dir.join("badly_formatted.css");
+  let badly_formatted_css = t.path().join("badly_formatted.css");
+  badly_formatted_original_css.copy(&badly_formatted_css);
+
   let fixed_ipynb = testdata_fmt_dir.join("badly_formatted_fixed.ipynb");
   let badly_formatted_original_ipynb =
     testdata_fmt_dir.join("badly_formatted.ipynb");
@@ -49,12 +55,13 @@ fn fmt_test() {
     .current_dir(&testdata_fmt_dir)
     .args_vec(vec![
       "fmt".to_string(),
+      "--unstable-css".to_string(),
       "--unstable-yaml".to_string(),
       format!(
-        "--ignore={badly_formatted_js},{badly_formatted_md},{badly_formatted_json},{badly_formatted_yaml},{badly_formatted_ipynb}",
+        "--ignore={badly_formatted_js},{badly_formatted_md},{badly_formatted_json},{badly_formatted_css},{badly_formatted_yaml},{badly_formatted_ipynb}",
       ),
       format!(
-        "--check {badly_formatted_js} {badly_formatted_md} {badly_formatted_json} {badly_formatted_yaml} {badly_formatted_ipynb}",
+        "--check {badly_formatted_js} {badly_formatted_md} {badly_formatted_json} {badly_formatted_css} {badly_formatted_yaml} {badly_formatted_ipynb}",
       ),
     ])
     .run();
@@ -70,10 +77,12 @@ fn fmt_test() {
     .args_vec(vec![
       "fmt".to_string(),
       "--check".to_string(),
+      "--unstable-css".to_string(),
       "--unstable-yaml".to_string(),
       badly_formatted_js.to_string(),
       badly_formatted_md.to_string(),
       badly_formatted_json.to_string(),
+      badly_formatted_css.to_string(),
       badly_formatted_yaml.to_string(),
       badly_formatted_ipynb.to_string(),
     ])
@@ -88,10 +97,12 @@ fn fmt_test() {
     .current_dir(&testdata_fmt_dir)
     .args_vec(vec![
       "fmt".to_string(),
+      "--unstable-css".to_string(),
       "--unstable-yaml".to_string(),
       badly_formatted_js.to_string(),
       badly_formatted_md.to_string(),
       badly_formatted_json.to_string(),
+      badly_formatted_css.to_string(),
       badly_formatted_yaml.to_string(),
       badly_formatted_ipynb.to_string(),
     ])
@@ -103,16 +114,19 @@ fn fmt_test() {
   let expected_js = fixed_js.read_to_string();
   let expected_md = fixed_md.read_to_string();
   let expected_json = fixed_json.read_to_string();
+  let expected_css = fixed_css.read_to_string();
   let expected_yaml = fixed_yaml.read_to_string();
   let expected_ipynb = fixed_ipynb.read_to_string();
   let actual_js = badly_formatted_js.read_to_string();
   let actual_md = badly_formatted_md.read_to_string();
   let actual_json = badly_formatted_json.read_to_string();
+  let actual_css = badly_formatted_css.read_to_string();
   let actual_yaml = badly_formatted_yaml.read_to_string();
   let actual_ipynb = badly_formatted_ipynb.read_to_string();
   assert_eq!(expected_js, actual_js);
   assert_eq!(expected_md, actual_md);
   assert_eq!(expected_json, actual_json);
+  assert_eq!(expected_css, actual_css);
   assert_eq!(expected_yaml, actual_yaml);
   assert_eq!(expected_ipynb, actual_ipynb);
 }
diff --git a/tests/specs/fmt/unstable_css/__test__.jsonc b/tests/specs/fmt/unstable_css/__test__.jsonc
new file mode 100644
index 00000000000000..32259f3ae4e8c6
--- /dev/null
+++ b/tests/specs/fmt/unstable_css/__test__.jsonc
@@ -0,0 +1,25 @@
+{
+  "tempDir": true,
+  "tests": {
+    "nothing": {
+      "args": "fmt",
+      "output": "Checked 1 file\n"
+    },
+    "flag": {
+      "args": "fmt --unstable-css",
+      "output": "[WILDLINE]badly_formatted.css\nChecked 1 file\n"
+    },
+    "config_file": {
+      "steps": [{
+        "args": [
+          "eval",
+          "Deno.writeTextFile('deno.json', '{\\n  \"unstable\": [\"fmt-css\"]\\n}\\n')"
+        ],
+        "output": "[WILDCARD]"
+      }, {
+        "args": "fmt",
+        "output": "[WILDLINE]badly_formatted.css\nChecked 2 files\n"
+      }]
+    }
+  }
+}
diff --git a/tests/specs/fmt/unstable_css/badly_formatted.css b/tests/specs/fmt/unstable_css/badly_formatted.css
new file mode 100644
index 00000000000000..e57adb7969ae61
--- /dev/null
+++ b/tests/specs/fmt/unstable_css/badly_formatted.css
@@ -0,0 +1 @@
+#app>.btn{ color : #000 }
diff --git a/tests/testdata/fmt/badly_formatted.css b/tests/testdata/fmt/badly_formatted.css
new file mode 100644
index 00000000000000..bfe18b82183d09
--- /dev/null
+++ b/tests/testdata/fmt/badly_formatted.css
@@ -0,0 +1,2 @@
+#app>.btn{ color : #000 }
+
diff --git a/tests/testdata/fmt/badly_formatted.md b/tests/testdata/fmt/badly_formatted.md
index 05a4b2f97cf78f..29d73b365da35f 100644
--- a/tests/testdata/fmt/badly_formatted.md
+++ b/tests/testdata/fmt/badly_formatted.md
@@ -32,7 +32,7 @@ function foo(): number {
 {
   // Comment in JSON
   "key":          "value",
-                "key2":      
+                "key2":
                 "value2",
 }
 
@@ -49,3 +49,7 @@ function foo(): number {
 -  item1
 -  item2
 ```
+
+```css
+#app>.btn{ color : #000 }
+```
diff --git a/tests/testdata/fmt/badly_formatted_fixed.css b/tests/testdata/fmt/badly_formatted_fixed.css
new file mode 100644
index 00000000000000..1653551f472f19
--- /dev/null
+++ b/tests/testdata/fmt/badly_formatted_fixed.css
@@ -0,0 +1,3 @@
+#app > .btn {
+  color: #000;
+}
diff --git a/tests/testdata/fmt/badly_formatted_fixed.md b/tests/testdata/fmt/badly_formatted_fixed.md
index 7a7d1913b7ef9f..db2afc809458c9 100644
--- a/tests/testdata/fmt/badly_formatted_fixed.md
+++ b/tests/testdata/fmt/badly_formatted_fixed.md
@@ -40,3 +40,9 @@ function foo(): number {
 - item1
 - item2
 ```
+
+```css
+#app > .btn {
+  color: #000;
+}
+```