diff --git a/keyboards/keebio/bdn9/rev4/config.h b/keyboards/keebio/bdn9/rev4/config.h
new file mode 100644
index 00000000000..7e66d32c74a
--- /dev/null
+++ b/keyboards/keebio/bdn9/rev4/config.h
@@ -0,0 +1,11 @@
+// Copyright 2026 Keebio (@keebio)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+/* Defines for the RGB matrix */
+#define WS2812_PWM_DRIVER PWMD15                   // TIM15
+#define WS2812_PWM_CHANNEL 2                       // TIM15_CH2
+#define WS2812_PWM_PAL_MODE 14                     // PB15 AF14 = TIM15_CH2
+#define WS2812_PWM_DMA_STREAM STM32_DMA1_STREAM5   // DMA1 Channel 5
+#define WS2812_PWM_DMA_CHANNEL 7                   // CSELR C5S = 7: TIM15_UP
diff --git a/keyboards/keebio/bdn9/rev4/halconf.h b/keyboards/keebio/bdn9/rev4/halconf.h
new file mode 100644
index 00000000000..2679567d91f
--- /dev/null
+++ b/keyboards/keebio/bdn9/rev4/halconf.h
@@ -0,0 +1,8 @@
+// Copyright 2026 Keebio (@keebio)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#define HAL_USE_PWM TRUE
+
+#include_next <halconf.h>
diff --git a/keyboards/keebio/bdn9/rev4/keyboard.json b/keyboards/keebio/bdn9/rev4/keyboard.json
new file mode 100644
index 00000000000..da3b34f2bc9
--- /dev/null
+++ b/keyboards/keebio/bdn9/rev4/keyboard.json
@@ -0,0 +1,97 @@
+{
+    "keyboard_name": "BDN9 Rev. 4",
+    "bootloader": "stm32-dfu",
+    "encoder": {
+        "rotary": [
+            {"pin_a": "B10", "pin_b": "B11"},
+            {"pin_a": "B3", "pin_b": "A15"},
+            {"pin_a": "A10", "pin_b": "A9"}
+        ]
+    },
+    "features": {
+        "bootmagic": true,
+        "command": true,
+        "console": true,
+        "encoder": true,
+        "extrakey": true,
+        "mousekey": true,
+        "rgb_matrix": true
+    },
+    "matrix_pins": {
+        "direct": [
+            ["B12", "B5", "B6"],
+            ["B14", "B4", "B7"],
+            ["A3", "A1", "A0"]
+        ]
+    },
+    "processor": "STM32L443",
+    "rgb_matrix": {
+        "animations": {
+            "alphas_mods": true,
+            "band_pinwheel_sat": true,
+            "band_pinwheel_val": true,
+            "band_sat": true,
+            "band_spiral_sat": true,
+            "band_spiral_val": true,
+            "band_val": true,
+            "breathing": true,
+            "cycle_all": true,
+            "cycle_left_right": true,
+            "cycle_out_in": true,
+            "cycle_out_in_dual": true,
+            "cycle_pinwheel": true,
+            "cycle_spiral": true,
+            "cycle_up_down": true,
+            "digital_rain": true,
+            "dual_beacon": true,
+            "gradient_left_right": true,
+            "gradient_up_down": true,
+            "hue_breathing": true,
+            "hue_pendulum": true,
+            "hue_wave": true,
+            "jellybean_raindrops": true,
+            "multisplash": true,
+            "pixel_flow": true,
+            "pixel_fractal": true,
+            "pixel_rain": true,
+            "rainbow_beacon": true,
+            "rainbow_moving_chevron": true,
+            "rainbow_pinwheels": true,
+            "raindrops": true,
+            "solid_multisplash": true,
+            "solid_reactive": true,
+            "solid_reactive_cross": true,
+            "solid_reactive_multicross": true,
+            "solid_reactive_multinexus": true,
+            "solid_reactive_multiwide": true,
+            "solid_reactive_nexus": true,
+            "solid_reactive_simple": true,
+            "solid_reactive_wide": true,
+            "solid_splash": true,
+            "splash": true,
+            "typing_heatmap": true
+        },
+        "driver": "ws2812",
+        "layout": [
+            {"matrix": [0, 0], "x": 80, "y": 0, "flags": 4},
+            {"matrix": [0, 1], "x": 112, "y": 0, "flags": 4},
+            {"matrix": [0, 2], "x": 144, "y": 0, "flags": 4},
+            {"matrix": [1, 2], "x": 144, "y": 32, "flags": 4},
+            {"matrix": [1, 1], "x": 112, "y": 32, "flags": 4},
+            {"matrix": [1, 0], "x": 80, "y": 32, "flags": 4},
+            {"x": 76, "y": 64, "flags": 2},
+            {"matrix": [2, 0], "x": 80, "y": 64, "flags": 4},
+            {"matrix": [2, 1], "x": 112, "y": 64, "flags": 4},
+            {"matrix": [2, 2], "x": 144, "y": 64, "flags": 4},
+            {"x": 148, "y": 64, "flags": 2}
+        ]
+    },
+    "usb": {
+        "device_version": "3.0.0",
+        "pid": "0x4133"
+    },
+    "ws2812": {
+        "driver": "pwm",
+        "pin": "B15"
+    }
+}
diff --git a/keyboards/keebio/bdn9/rev4/mcuconf.h b/keyboards/keebio/bdn9/rev4/mcuconf.h
new file mode 100644
index 00000000000..b26b8ba3c57
--- /dev/null
+++ b/keyboards/keebio/bdn9/rev4/mcuconf.h
@@ -0,0 +1,10 @@
+// Copyright 2026 Keebio (@keebio)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include_next <mcuconf.h>
+
+/* enable TIM15, used for RGB LED PWM driver */
+#undef STM32_PWM_USE_TIM15
+#define STM32_PWM_USE_TIM15 TRUE
diff --git a/keyboards/keebio/bdn9/rev4/rev4.c b/keyboards/keebio/bdn9/rev4/rev4.c
new file mode 100644
index 00000000000..5dcb721c09c
--- /dev/null
+++ b/keyboards/keebio/bdn9/rev4/rev4.c
@@ -0,0 +1,30 @@
+// Copyright 2026 Keebio (@keebio)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "quantum.h"
+
+bool encoder_update_kb(uint8_t index, bool clockwise) {
+    if (!encoder_update_user(index, clockwise)) { return false; }
+    if (index == 0) {
+        if (clockwise) {
+            tap_code(KC_VOLU);
+        } else {
+            tap_code(KC_VOLD);
+        }
+    }
+    else if (index == 1) {
+        if (clockwise) {
+            tap_code(KC_DOWN);
+        } else {
+            tap_code(KC_UP);
+        }
+    }
+    else if (index == 2) {
+        if (clockwise) {
+            tap_code(KC_PGDN);
+        } else {
+            tap_code(KC_PGUP);
+        }
+    }
+    return false;
+}