diff --git a/CHANGELOG.md b/CHANGELOG.md
index 870cdd7ae1..6747c9fce2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@
 ### Client
 - Feat: 新しいゲームを追加
 - Feat: 絵文字の詳細ダイアログを追加
+- Feat: 枠線をつけるMFM`$[border.width=1,style=solid,color=fff,radius=0 ...]`を追加
 - Enhance: ハッシュタグ入力時に、本文の末尾の行に何も書かれていない場合は新たにスペースを追加しないように
 - Enhance: チャンネルノートのピン留めをノートのメニューからできるように
 - Enhance: 管理者の場合はAPI tokenの発行画面で管理機能に関する権限を付与できるように
diff --git a/packages/frontend/src/components/global/MkMisskeyFlavoredMarkdown.ts b/packages/frontend/src/components/global/MkMisskeyFlavoredMarkdown.ts
index 650c79dff7..f55069200d 100644
--- a/packages/frontend/src/components/global/MkMisskeyFlavoredMarkdown.ts
+++ b/packages/frontend/src/components/global/MkMisskeyFlavoredMarkdown.ts
@@ -61,7 +61,12 @@ export default function(props: MfmProps, context: SetupContext<MfmEvents>) {
 		if (t == null) return null;
 		return t.match(/^[0-9.]+s$/) ? t : null;
 	};
-
+	
+	const validColor = (c: string | null | undefined): string | null => {
+		if (c == null) return null;
+		return c.match(/^[0-9a-f]{3,6}$/i) ? c : null;
+	};
+	
 	const useAnim = defaultStore.state.advancedMfm && defaultStore.state.animatedMfm;
 
 	/**
@@ -240,17 +245,30 @@ export default function(props: MfmProps, context: SetupContext<MfmEvents>) {
 						break;
 					}
 					case 'fg': {
-						let color = token.props.args.color;
-						if (!/^[0-9a-f]{3,6}$/i.test(color)) color = 'f00';
+						let color = validColor(token.props.args.color);
+						color = color ?? 'f00';
 						style = `color: #${color}; overflow-wrap: anywhere;`;
 						break;
 					}
 					case 'bg': {
-						let color = token.props.args.color;
-						if (!/^[0-9a-f]{3,6}$/i.test(color)) color = 'f00';
+						let color = validColor(token.props.args.color);
+						color = color ?? 'f00';
 						style = `background-color: #${color}; overflow-wrap: anywhere;`;
 						break;
 					}
+					case 'border': {
+						let color = validColor(token.props.args.color);
+						color = color ? `#${color}` : 'var(--accent)';
+						let b_style = token.props.args.style;
+						if (
+							!['hidden', 'dotted', 'dashed', 'solid', 'double', 'groove', 'ridge', 'inset', 'outset']
+								.includes(b_style)
+						) b_style = 'solid';
+						const width = parseFloat(token.props.args.width ?? '1');
+						const radius = parseFloat(token.props.args.radius ?? '0');
+						style = `border: ${width}px ${b_style} ${color}; border-radius: ${radius}px`;
+						break;
+					}
 					case 'ruby': {
 						if (token.children.length === 1) {
 							const child = token.children[0];
diff --git a/packages/frontend/src/const.ts b/packages/frontend/src/const.ts
index 01c224ae2d..ea07204456 100644
--- a/packages/frontend/src/const.ts
+++ b/packages/frontend/src/const.ts
@@ -108,4 +108,4 @@ export const DEFAULT_SERVER_ERROR_IMAGE_URL = 'https://xn--931a.moe/assets/error
 export const DEFAULT_NOT_FOUND_IMAGE_URL = 'https://xn--931a.moe/assets/not-found.jpg';
 export const DEFAULT_INFO_IMAGE_URL = 'https://xn--931a.moe/assets/info.jpg';
 
-export const MFM_TAGS = ['tada', 'jelly', 'twitch', 'shake', 'spin', 'jump', 'bounce', 'flip', 'x2', 'x3', 'x4', 'scale', 'position', 'fg', 'bg', 'font', 'blur', 'rainbow', 'sparkle', 'rotate', 'ruby', 'unixtime'];
+export const MFM_TAGS = ['tada', 'jelly', 'twitch', 'shake', 'spin', 'jump', 'bounce', 'flip', 'x2', 'x3', 'x4', 'scale', 'position', 'fg', 'bg', 'border', 'font', 'blur', 'rainbow', 'sparkle', 'rotate', 'ruby', 'unixtime'];