diff --git a/harper-cli/src/main.rs b/harper-cli/src/main.rs
index 68cd2ce9d..45440d40a 100644
--- a/harper-cli/src/main.rs
+++ b/harper-cli/src/main.rs
@@ -63,9 +63,9 @@ enum Args {
         /// Overlapping lints are removed by default. This option disables that behavior.
         #[arg(short = 'o', long)]
         keep_overlapping_lints: bool,
-        /// Specify the dialect.
-        #[arg(short, long, default_value = Dialect::American.to_string())]
-        dialect: Dialect,
+        /// Specify the dialect. Common synonyms, abbreviations, and codes are supported.
+        #[arg(short, long, default_value = "us")]
+        dialect: String,
         /// Path to the user dictionary.
         #[arg(short, long, default_value = config_dir().unwrap().join("harper-ls/dictionary.txt").into_os_string())]
         user_dict_path: PathBuf,
@@ -211,11 +211,13 @@ fn main() -> anyhow::Result<()> {
             ignore,
             only,
             keep_overlapping_lints,
-            dialect,
+            dialect: dialect_str,
             user_dict_path,
-            // TODO workspace_dict_path?
             file_dict_path,
         } => {
+            let dialect = parse_dialect(&dialect_str)
+                .map_err(|e| anyhow!("Invalid dialect '{}': {}", dialect_str, e))?;
+
             lint(
                 markdown_options,
                 curated_dictionary,
@@ -945,6 +947,19 @@ fn main() -> anyhow::Result<()> {
     }
 }
 
+/// Parse a dialect string into a Dialect enum value.
+/// Supports common synonyms, abbreviations, and codes.
+fn parse_dialect(dialect: &str) -> anyhow::Result<Dialect> {
+    match dialect.to_lowercase().as_str() {
+        "us" | "usa" | "america" | "american" | "en-us" | "en_us" => Ok(Dialect::American),
+        "uk" | "gb" | "british" | "britain" | "en-gb" | "en_gb" => Ok(Dialect::British),
+        "au" | "aus" | "australia" | "australian" | "en-au" | "en_au" => Ok(Dialect::Australian),
+        "in" | "india" | "indian" | "bharat" | "en-in" | "en_in" => Ok(Dialect::Indian),
+        "ca" | "canada" | "canadian" | "en-ca" | "en_ca" => Ok(Dialect::Canadian),
+        _ => Err(anyhow!("Unknown dialect: {}", dialect)),
+    }
+}
+
 /// Split a dictionary line into its word and annotation segments
 fn line_to_parts(line: &str) -> (String, String) {
     if let Some((word, annot)) = line.split_once('/') {