diff --git a/locales/en-US.yml b/locales/en-US.yml
index 9c02e83021..faa7f5e59e 100644
--- a/locales/en-US.yml
+++ b/locales/en-US.yml
@@ -3194,6 +3194,7 @@ _imageEffector:
     mirror: "Mirror"
     invert: "Invert Colors"
     grayscale: "Grayscale"
+    blur: "Blur"
     colorAdjust: "Color Correction"
     colorClamp: "Color Compression"
     colorClampAdvanced: "Color Compression (Advanced)"
@@ -3209,6 +3210,8 @@ _imageEffector:
     angle: "Angle"
     scale: "Size"
     size: "Size"
+    radius: "Radius"
+    samples: "Samples"
     color: "Color"
     opacity: "Opacity"
     normalize: "Normalize"
diff --git a/locales/index.d.ts b/locales/index.d.ts
index 95886125ff..9bef0113a2 100644
--- a/locales/index.d.ts
+++ b/locales/index.d.ts
@@ -12346,6 +12346,10 @@ export interface Locale extends ILocale {
              * 白黒
              */
             "grayscale": string;
+            /**
+             * ぼかし
+             */
+            "blur": string;
             /**
              * 色調補正
              */
@@ -12391,9 +12395,9 @@ export interface Locale extends ILocale {
              */
             "tearing": string;
             /**
-             * 塗りつぶし(四角)
+             * 塗りつぶし
              */
-            "fillSquare": string;
+            "fill": string;
         };
         "_fxProps": {
             /**
@@ -12408,6 +12412,14 @@ export interface Locale extends ILocale {
              * サイズ
              */
             "size": string;
+            /**
+             * 半径
+             */
+            "radius": string;
+            /**
+             * サンプル数
+             */
+            "samples": string;
             /**
              * 位置
              */
@@ -12524,6 +12536,10 @@ export interface Locale extends ILocale {
              * 黒色にする
              */
             "zoomLinesBlack": string;
+            /**
+             * 円形
+             */
+            "circle": string;
         };
     };
     /**
diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index 4ae52990e5..b0d864ade8 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -3306,6 +3306,7 @@ _imageEffector:
     mirror: "ミラー"
     invert: "色の反転"
     grayscale: "白黒"
+    blur: "ぼかし"
     colorAdjust: "色調補正"
     colorClamp: "色の圧縮"
     colorClampAdvanced: "色の圧縮(高度)"
@@ -3317,12 +3318,14 @@ _imageEffector:
     checker: "チェッカー"
     blockNoise: "ブロックノイズ"
     tearing: "ティアリング"
-    fillSquare: "塗りつぶし(四角)"
+    fill: "塗りつぶし"
 
   _fxProps:
     angle: "角度"
     scale: "サイズ"
     size: "サイズ"
+    radius: "半径"
+    samples: "サンプル数"
     offset: "位置"
     color: "色"
     opacity: "不透明度"
@@ -3352,6 +3355,7 @@ _imageEffector:
     zoomLinesThreshold: "集中線の幅"
     zoomLinesMaskSize: "中心径"
     zoomLinesBlack: "黒色にする"
+    circle: "円形"
 
 drafts: "下書き"
 _drafts:
diff --git a/packages/frontend/src/components/MkImageEffectorDialog.vue b/packages/frontend/src/components/MkImageEffectorDialog.vue
index 465100ef20..96fb01bb8c 100644
--- a/packages/frontend/src/components/MkImageEffectorDialog.vue
+++ b/packages/frontend/src/components/MkImageEffectorDialog.vue
@@ -23,7 +23,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 				<div :class="$style.previewContainer">
 					<div class="_acrylic" :class="$style.previewTitle">{{ i18n.ts.preview }}</div>
 					<div class="_acrylic" :class="$style.editControls">
-						<button class="_button" :class="[$style.previewControlsButton, fillSquare ? $style.active : null]" @click="fillSquare = true"><i class="ti ti-pencil"></i></button>
+						<button class="_button" :class="[$style.previewControlsButton, penMode != null ? $style.active : null]" @click="showPenMenu"><i class="ti ti-pencil"></i></button>
 					</div>
 					<div class="_acrylic" :class="$style.previewControls">
 						<button class="_button" :class="[$style.previewControlsButton, !enabled ? $style.active : null]" @click="enabled = false">Before</button>
@@ -216,10 +216,24 @@ watch(enabled, () => {
 	}
 });
 
-const fillSquare = ref(false);
+const penMode = ref<'fill' | 'blur' | null>(null);
+
+function showPenMenu(ev: MouseEvent) {
+	os.popupMenu([{
+		text: i18n.ts._imageEffector._fxs.fill,
+		action: () => {
+			penMode.value = 'fill';
+		},
+	}, {
+		text: i18n.ts._imageEffector._fxs.blur,
+		action: () => {
+			penMode.value = 'blur';
+		},
+	}], ev.currentTarget ?? ev.target);
+}
 
 function onImagePointerdown(ev: PointerEvent) {
-	if (canvasEl.value == null || imageBitmap == null || !fillSquare.value) return;
+	if (canvasEl.value == null || imageBitmap == null || penMode.value == null) return;
 
 	const AW = canvasEl.value.clientWidth;
 	const AH = canvasEl.value.clientHeight;
@@ -250,19 +264,34 @@ function onImagePointerdown(ev: PointerEvent) {
 	}
 
 	const id = genId();
-	layers.push({
-		id,
-		fxId: 'fillSquare',
-		params: {
-			offsetX: 0,
-			offsetY: 0,
-			scaleX: 0.1,
-			scaleY: 0.1,
-			angle: 0,
-			opacity: 1,
-			color: [1, 1, 1],
-		},
-	});
+	if (penMode.value === 'fill') {
+		layers.push({
+			id,
+			fxId: 'fill',
+			params: {
+				offsetX: 0,
+				offsetY: 0,
+				scaleX: 0.1,
+				scaleY: 0.1,
+				angle: 0,
+				opacity: 1,
+				color: [1, 1, 1],
+			},
+		});
+	} else if (penMode.value === 'blur') {
+		layers.push({
+			id,
+			fxId: 'blur',
+			params: {
+				offsetX: 0,
+				offsetY: 0,
+				scaleX: 0.1,
+				scaleY: 0.1,
+				angle: 0,
+				radius: 3,
+			},
+		});
+	}
 
 	_move(ev.offsetX, ev.offsetY);
 
@@ -302,7 +331,7 @@ function onImagePointerdown(ev: PointerEvent) {
 		canvasEl.value?.removeEventListener('pointercancel', up);
 		canvasEl.value?.releasePointerCapture(ev.pointerId);
 
-		fillSquare.value = false;
+		penMode.value = null;
 	}
 
 	canvasEl.value.addEventListener('pointermove', move);
diff --git a/packages/frontend/src/utility/image-effector/fxs.ts b/packages/frontend/src/utility/image-effector/fxs.ts
index 43e10a22fc..83ec20823d 100644
--- a/packages/frontend/src/utility/image-effector/fxs.ts
+++ b/packages/frontend/src/utility/image-effector/fxs.ts
@@ -18,7 +18,8 @@ import { FX_stripe } from './fxs/stripe.js';
 import { FX_threshold } from './fxs/threshold.js';
 import { FX_zoomLines } from './fxs/zoomLines.js';
 import { FX_blockNoise } from './fxs/blockNoise.js';
-import { FX_fillSquare } from './fxs/fillSquare.js';
+import { FX_fill } from './fxs/fill.js';
+import { FX_blur } from './fxs/blur.js';
 import type { ImageEffectorFx } from './ImageEffector.js';
 
 export const FXS = [
@@ -37,5 +38,6 @@ export const FXS = [
 	FX_chromaticAberration,
 	FX_tearing,
 	FX_blockNoise,
-	FX_fillSquare,
+	FX_fill,
+	FX_blur,
 ] as const satisfies ImageEffectorFx<string, any>[];
diff --git a/packages/frontend/src/utility/image-effector/fxs/blur.ts b/packages/frontend/src/utility/image-effector/fxs/blur.ts
new file mode 100644
index 0000000000..fa215fd3e4
--- /dev/null
+++ b/packages/frontend/src/utility/image-effector/fxs/blur.ts
@@ -0,0 +1,157 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { defineImageEffectorFx } from '../ImageEffector.js';
+import { i18n } from '@/i18n.js';
+
+const shader = `#version 300 es
+precision mediump float;
+
+const float PI = 3.141592653589793;
+const float TWO_PI = 6.283185307179586;
+const float HALF_PI = 1.5707963267948966;
+
+in vec2 in_uv;
+uniform sampler2D in_texture;
+uniform vec2 in_resolution;
+uniform vec2 u_offset;
+uniform vec2 u_scale;
+uniform bool u_ellipse;
+uniform float u_angle;
+uniform float u_radius;
+uniform int u_samples;
+out vec4 out_color;
+
+void main() {
+	float angle = -(u_angle * PI);
+	vec2 centeredUv = in_uv - vec2(0.5, 0.5) - u_offset;
+	vec2 rotatedUV = vec2(
+		centeredUv.x * cos(angle) - centeredUv.y * sin(angle),
+		centeredUv.x * sin(angle) + centeredUv.y * cos(angle)
+	) + u_offset;
+
+	bool isInside = false;
+	if (u_ellipse) {
+		vec2 norm = (rotatedUV - u_offset) / u_scale;
+		isInside = dot(norm, norm) <= 1.0;
+	} else {
+		isInside = rotatedUV.x > u_offset.x - u_scale.x && rotatedUV.x < u_offset.x + u_scale.x && rotatedUV.y > u_offset.y - u_scale.y && rotatedUV.y < u_offset.y + u_scale.y;
+	}
+
+	if (!isInside) {
+		out_color = texture(in_texture, in_uv);
+		return;
+	}
+
+	vec4 result = vec4(0.0);
+	float totalSamples = 0.0;
+
+	// Make blur radius resolution-independent by using a percentage of image size
+	// This ensures consistent visual blur regardless of image resolution
+	float referenceSize = min(in_resolution.x, in_resolution.y);
+	float normalizedRadius = u_radius / 100.0; // Convert radius to percentage (0-15 -> 0-0.15)
+	vec2 blurOffset = vec2(normalizedRadius) / in_resolution * referenceSize;
+
+	// Calculate how many samples to take in each direction
+	// This determines the grid density, not the blur extent
+	int sampleRadius = int(sqrt(float(u_samples)) / 2.0);
+
+	// Sample in a grid pattern within the specified radius
+	for (int x = -sampleRadius; x <= sampleRadius; x++) {
+		for (int y = -sampleRadius; y <= sampleRadius; y++) {
+			// Normalize the grid position to [-1, 1] range
+			float normalizedX = float(x) / float(sampleRadius);
+			float normalizedY = float(y) / float(sampleRadius);
+
+			// Scale by radius to get the actual sampling offset
+			vec2 offset = vec2(normalizedX, normalizedY) * blurOffset;
+			vec2 sampleUV = in_uv + offset;
+
+			// Only sample if within texture bounds
+			if (sampleUV.x >= 0.0 && sampleUV.x <= 1.0 && sampleUV.y >= 0.0 && sampleUV.y <= 1.0) {
+				result += texture(in_texture, sampleUV);
+				totalSamples += 1.0;
+			}
+		}
+	}
+
+	out_color = totalSamples > 0.0 ? result / totalSamples : texture(in_texture, in_uv);
+}
+`;
+
+export const FX_blur = defineImageEffectorFx({
+	id: 'blur',
+	name: i18n.ts._imageEffector._fxs.blur,
+	shader,
+	uniforms: ['offset', 'scale', 'ellipse', 'angle', 'radius', 'samples'] as const,
+	params: {
+		offsetX: {
+			label: i18n.ts._imageEffector._fxProps.offset + ' X',
+			type: 'number',
+			default: 0.0,
+			min: -1.0,
+			max: 1.0,
+			step: 0.01,
+			toViewValue: v => Math.round(v * 100) + '%',
+		},
+		offsetY: {
+			label: i18n.ts._imageEffector._fxProps.offset + ' Y',
+			type: 'number',
+			default: 0.0,
+			min: -1.0,
+			max: 1.0,
+			step: 0.01,
+			toViewValue: v => Math.round(v * 100) + '%',
+		},
+		scaleX: {
+			label: i18n.ts._imageEffector._fxProps.scale + ' W',
+			type: 'number',
+			default: 0.5,
+			min: 0.0,
+			max: 1.0,
+			step: 0.01,
+			toViewValue: v => Math.round(v * 100) + '%',
+		},
+		scaleY: {
+			label: i18n.ts._imageEffector._fxProps.scale + ' H',
+			type: 'number',
+			default: 0.5,
+			min: 0.0,
+			max: 1.0,
+			step: 0.01,
+			toViewValue: v => Math.round(v * 100) + '%',
+		},
+		ellipse: {
+			label: i18n.ts._imageEffector._fxProps.circle,
+			type: 'boolean',
+			default: false,
+		},
+		angle: {
+			label: i18n.ts._imageEffector._fxProps.angle,
+			type: 'number',
+			default: 0,
+			min: -1.0,
+			max: 1.0,
+			step: 0.01,
+			toViewValue: v => Math.round(v * 90) + '°',
+		},
+		radius: {
+			label: i18n.ts._imageEffector._fxProps.strength,
+			type: 'number',
+			default: 3.0,
+			min: 0.0,
+			max: 10.0,
+			step: 0.5,
+		},
+	},
+	main: ({ gl, u, params }) => {
+		gl.uniform2f(u.offset, params.offsetX / 2, params.offsetY / 2);
+		gl.uniform2f(u.scale, params.scaleX / 2, params.scaleY / 2);
+		gl.uniform1i(u.ellipse, params.ellipse ? 1 : 0);
+		gl.uniform1f(u.angle, params.angle / 2);
+		gl.uniform1f(u.radius, params.radius);
+		gl.uniform1i(u.samples, 256);
+	},
+});
diff --git a/packages/frontend/src/utility/image-effector/fxs/fillSquare.ts b/packages/frontend/src/utility/image-effector/fxs/fill.ts
similarity index 77%
rename from packages/frontend/src/utility/image-effector/fxs/fillSquare.ts
rename to packages/frontend/src/utility/image-effector/fxs/fill.ts
index 55b53830e0..35dee594e3 100644
--- a/packages/frontend/src/utility/image-effector/fxs/fillSquare.ts
+++ b/packages/frontend/src/utility/image-effector/fxs/fill.ts
@@ -18,6 +18,7 @@ uniform sampler2D in_texture;
 uniform vec2 in_resolution;
 uniform vec2 u_offset;
 uniform vec2 u_scale;
+uniform bool u_ellipse;
 uniform float u_angle;
 uniform vec3 u_color;
 uniform float u_opacity;
@@ -35,7 +36,13 @@ void main() {
 		centeredUv.x * sin(angle) + centeredUv.y * cos(angle)
 	) + u_offset;
 
-	bool isInside = rotatedUV.x > u_offset.x - u_scale.x && rotatedUV.x < u_offset.x + u_scale.x && rotatedUV.y > u_offset.y - u_scale.y && rotatedUV.y < u_offset.y + u_scale.y;
+	bool isInside = false;
+	if (u_ellipse) {
+		vec2 norm = (rotatedUV - u_offset) / u_scale;
+		isInside = dot(norm, norm) <= 1.0;
+	} else {
+		isInside = rotatedUV.x > u_offset.x - u_scale.x && rotatedUV.x < u_offset.x + u_scale.x && rotatedUV.y > u_offset.y - u_scale.y && rotatedUV.y < u_offset.y + u_scale.y;
+	}
 
 	out_color = isInside ? vec4(
 		mix(in_color.r, u_color.r, u_opacity),
@@ -46,11 +53,11 @@ void main() {
 }
 `;
 
-export const FX_fillSquare = defineImageEffectorFx({
-	id: 'fillSquare',
-	name: i18n.ts._imageEffector._fxs.fillSquare,
+export const FX_fill = defineImageEffectorFx({
+	id: 'fill',
+	name: i18n.ts._imageEffector._fxs.fill,
 	shader,
-	uniforms: ['offset', 'scale', 'angle', 'color', 'opacity'] as const,
+	uniforms: ['offset', 'scale', 'ellipse', 'angle', 'color', 'opacity'] as const,
 	params: {
 		offsetX: {
 			label: i18n.ts._imageEffector._fxProps.offset + ' X',
@@ -71,7 +78,7 @@ export const FX_fillSquare = defineImageEffectorFx({
 			toViewValue: v => Math.round(v * 100) + '%',
 		},
 		scaleX: {
-			label: i18n.ts._imageEffector._fxProps.scale + ' X',
+			label: i18n.ts._imageEffector._fxProps.scale + ' W',
 			type: 'number',
 			default: 0.5,
 			min: 0.0,
@@ -80,7 +87,7 @@ export const FX_fillSquare = defineImageEffectorFx({
 			toViewValue: v => Math.round(v * 100) + '%',
 		},
 		scaleY: {
-			label: i18n.ts._imageEffector._fxProps.scale + ' Y',
+			label: i18n.ts._imageEffector._fxProps.scale + ' H',
 			type: 'number',
 			default: 0.5,
 			min: 0.0,
@@ -88,6 +95,11 @@ export const FX_fillSquare = defineImageEffectorFx({
 			step: 0.01,
 			toViewValue: v => Math.round(v * 100) + '%',
 		},
+		ellipse: {
+			label: i18n.ts._imageEffector._fxProps.circle,
+			type: 'boolean',
+			default: false,
+		},
 		angle: {
 			label: i18n.ts._imageEffector._fxProps.angle,
 			type: 'number',
@@ -115,6 +127,7 @@ export const FX_fillSquare = defineImageEffectorFx({
 	main: ({ gl, u, params }) => {
 		gl.uniform2f(u.offset, params.offsetX / 2, params.offsetY / 2);
 		gl.uniform2f(u.scale, params.scaleX / 2, params.scaleY / 2);
+		gl.uniform1i(u.ellipse, params.ellipse ? 1 : 0);
 		gl.uniform1f(u.angle, params.angle / 2);
 		gl.uniform3f(u.color, params.color[0], params.color[1], params.color[2]);
 		gl.uniform1f(u.opacity, params.opacity);