diff --git a/README.md b/README.md
index 6a236f47ef..f444da7a29 100644
--- a/README.md
+++ b/README.md
@@ -145,6 +145,7 @@ gitnexus clean --all --force     # Delete all indexes
 gitnexus wiki [path]             # Generate repository wiki from knowledge graph
 gitnexus wiki --model <model>    # Wiki with custom LLM model (default: gpt-4o-mini)
 gitnexus wiki --base-url <url>   # Wiki with custom LLM API base URL
+gitnexus wiki --language zh-CN   # Wiki in Chinese (or ja, ko, etc.)
 ```
 
 ### What Your AI Agent Gets
@@ -447,6 +448,10 @@ gitnexus wiki --base-url https://api.anthropic.com/v1
 
 # Force full regeneration
 gitnexus wiki --force
+
+# Generate wiki in a specific language
+gitnexus wiki --language zh-CN
+gitnexus wiki --language ja
 ```
 
 The wiki generator reads the indexed graph structure, groups files into modules via LLM, generates per-module documentation pages, and creates an overview page — all with cross-references to the knowledge graph.
diff --git a/gitnexus/src/cli/index.ts b/gitnexus/src/cli/index.ts
index 10268db837..ad88b578cd 100644
--- a/gitnexus/src/cli/index.ts
+++ b/gitnexus/src/cli/index.ts
@@ -74,6 +74,7 @@ program
   .option('--base-url <url>', 'LLM API base URL (default: OpenAI)')
   .option('--api-key <key>', 'LLM API key (saved to ~/.gitnexus/config.json)')
   .option('--concurrency <n>', 'Parallel LLM calls (default: 3)', '3')
+  .option('--language <lang>', 'Output language for wiki (e.g. zh-CN, ja, ko)')
   .option('--gist', 'Publish wiki as a public GitHub Gist after generation')
   .action(wikiCommand);
 
diff --git a/gitnexus/src/cli/wiki.ts b/gitnexus/src/cli/wiki.ts
index 70ab00785b..b8f28f4e67 100644
--- a/gitnexus/src/cli/wiki.ts
+++ b/gitnexus/src/cli/wiki.ts
@@ -20,6 +20,7 @@ export interface WikiCommandOptions {
   baseUrl?: string;
   apiKey?: string;
   concurrency?: string;
+  language?: string;
   gist?: boolean;
 }
 
@@ -242,6 +243,7 @@ export const wikiCommand = async (
     model: options?.model,
     baseUrl: options?.baseUrl,
     concurrency: options?.concurrency ? parseInt(options.concurrency, 10) : undefined,
+    language: options?.language,
   };
 
   const generator = new WikiGenerator(
diff --git a/gitnexus/src/core/wiki/generator.ts b/gitnexus/src/core/wiki/generator.ts
index 666dc6e463..4cb328ca5a 100644
--- a/gitnexus/src/core/wiki/generator.ts
+++ b/gitnexus/src/core/wiki/generator.ts
@@ -63,6 +63,7 @@ export interface WikiOptions {
   apiKey?: string;
   maxTokensPerModule?: number;
   concurrency?: number;
+  language?: string;
 }
 
 export interface WikiMeta {
@@ -97,6 +98,7 @@ export class WikiGenerator {
   private llmConfig: LLMConfig;
   private maxTokensPerModule: number;
   private concurrency: number;
+  private language?: string;
   private options: WikiOptions;
   private onProgress: ProgressCallback;
   private failedModules: string[] = [];
@@ -116,6 +118,7 @@ export class WikiGenerator {
     this.options = options;
     this.llmConfig = llmConfig;
     this.maxTokensPerModule = options.maxTokensPerModule ?? DEFAULT_MAX_TOKENS_PER_MODULE;
+    this.language = options.language;
     this.concurrency = options.concurrency ?? 3;
     const progressFn = onProgress || (() => {});
     this.onProgress = (phase, percent, detail) => {
@@ -488,7 +491,7 @@ export class WikiGenerator {
     });
 
     const response = await callLLM(
-      prompt, this.llmConfig, MODULE_SYSTEM_PROMPT,
+      prompt, this.llmConfig, this.withLanguage(MODULE_SYSTEM_PROMPT),
       this.streamOpts(node.name),
     );
 
@@ -531,7 +534,7 @@ export class WikiGenerator {
     });
 
     const response = await callLLM(
-      prompt, this.llmConfig, PARENT_SYSTEM_PROMPT,
+      prompt, this.llmConfig, this.withLanguage(PARENT_SYSTEM_PROMPT),
       this.streamOpts(node.name),
     );
 
@@ -578,7 +581,7 @@ export class WikiGenerator {
     });
 
     const response = await callLLM(
-      prompt, this.llmConfig, OVERVIEW_SYSTEM_PROMPT,
+      prompt, this.llmConfig, this.withLanguage(OVERVIEW_SYSTEM_PROMPT),
       this.streamOpts('Generating overview', 88),
     );
 
@@ -909,6 +912,14 @@ export class WikiGenerator {
     return null;
   }
 
+  /**
+   * Append a language instruction to the system prompt when --language is set.
+   */
+  private withLanguage(systemPrompt: string): string {
+    if (!this.language) return systemPrompt;
+    return `${systemPrompt}\n\nIMPORTANT: Write ALL documentation output in ${this.language}. Use ${this.language} for headings, descriptions, and explanations. Keep code identifiers, file paths, and Mermaid node labels in their original form.`;
+  }
+
   private slugify(name: string): string {
     return name
       .toLowerCase()