diff --git a/keyboards/25keys/cassette42/common/oled_helper.h b/keyboards/25keys/cassette42/common/oled_helper.h
index daeb7bfa4d..d677c2a872 100644
--- a/keyboards/25keys/cassette42/common/oled_helper.h
+++ b/keyboards/25keys/cassette42/common/oled_helper.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #ifdef OLED_ENABLE
 
 void render_logo(void);
diff --git a/keyboards/doio/kb16/lib/bongocat/bongocat.h b/keyboards/doio/kb16/lib/bongocat/bongocat.h
index 65ceabc682..2ffeca1993 100644
--- a/keyboards/doio/kb16/lib/bongocat/bongocat.h
+++ b/keyboards/doio/kb16/lib/bongocat/bongocat.h
@@ -14,4 +14,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_bongocat(void);
diff --git a/keyboards/doio/kb16/lib/layer_status/layer_status.h b/keyboards/doio/kb16/lib/layer_status/layer_status.h
index a367a829d7..2c4b08f25a 100644
--- a/keyboards/doio/kb16/lib/layer_status/layer_status.h
+++ b/keyboards/doio/kb16/lib/layer_status/layer_status.h
@@ -15,4 +15,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_layer_status(void);
diff --git a/keyboards/doio/kb16/lib/logo.h b/keyboards/doio/kb16/lib/logo.h
index 91d1ddce34..bb3ddc446e 100644
--- a/keyboards/doio/kb16/lib/logo.h
+++ b/keyboards/doio/kb16/lib/logo.h
@@ -15,4 +15,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_logo(void);
diff --git a/keyboards/gboards/engine/keymap_engine.h b/keyboards/gboards/engine/keymap_engine.h
index 599c1ca3e4..dfed493e21 100644
--- a/keyboards/gboards/engine/keymap_engine.h
+++ b/keyboards/gboards/engine/keymap_engine.h
@@ -7,6 +7,8 @@
  * With this disgusting bodge, you can just edit your .defs and compile!
  */
 
+#pragma once
+
 // Clear all X Macros
 #define PRES BLANK
 #define KEYS BLANK
diff --git a/keyboards/gboards/g/config_default.h b/keyboards/gboards/g/config_default.h
index 821c2c4ad5..56dd634d13 100644
--- a/keyboards/gboards/g/config_default.h
+++ b/keyboards/gboards/g/config_default.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #include "engine.h"
 
 // Configuration options for the engine
diff --git a/keyboards/gboards/g/keymap_combo.h b/keyboards/gboards/g/keymap_combo.h
index 68ea44b1b4..c062a298a5 100644
--- a/keyboards/gboards/g/keymap_combo.h
+++ b/keyboards/gboards/g/keymap_combo.h
@@ -1,3 +1,5 @@
+#pragma once
+
 // Keymap helpers
 // define reference layers per layer.
 #define REF_LAYER_FOR_LAYER(LAYER, REF_LAYER)   \
diff --git a/keyboards/gboards/g/keymap_engine.h b/keyboards/gboards/g/keymap_engine.h
index 055b5941e4..e134472da0 100644
--- a/keyboards/gboards/g/keymap_engine.h
+++ b/keyboards/gboards/g/keymap_engine.h
@@ -6,6 +6,9 @@
  * using a external generator (Like is done for the ASETNIOP base keymaps)
  * With this disgusting bodge, you can just edit your .defs and compile!
  */
+
+#pragma once
+
 #include "g/engine.h"
 
 // Clear all X Macros
diff --git a/keyboards/gopolar/gg86/lib/logo.h b/keyboards/gopolar/gg86/lib/logo.h
index 08ab8ea529..d1197b15f5 100644
--- a/keyboards/gopolar/gg86/lib/logo.h
+++ b/keyboards/gopolar/gg86/lib/logo.h
@@ -14,4 +14,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_logo(void);
diff --git a/keyboards/gopolar/gg86/lib/wave.h b/keyboards/gopolar/gg86/lib/wave.h
index f4e5e5052c..d87525c1d4 100644
--- a/keyboards/gopolar/gg86/lib/wave.h
+++ b/keyboards/gopolar/gg86/lib/wave.h
@@ -15,6 +15,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 extern const unsigned char font[] PROGMEM;
 
 #define ROW_1 OLED_DISPLAY_WIDTH
diff --git a/keyboards/handwired/d48/taphold.h b/keyboards/handwired/d48/taphold.h
index 3bc5ca0275..2a691aa63f 100644
--- a/keyboards/handwired/d48/taphold.h
+++ b/keyboards/handwired/d48/taphold.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #include "quantum.h"
 
 typedef enum taphold_mode_t {
diff --git a/keyboards/handwired/promethium/color.h b/keyboards/handwired/promethium/color.h
index 077242d5f1..2bbfcb83a7 100644
--- a/keyboards/handwired/promethium/color.h
+++ b/keyboards/handwired/promethium/color.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #define COLOR_BLANK       0, 0, 0
 
 #define COLOR_BLACK       0, 0, 0
diff --git a/keyboards/handwired/promethium/rgbsps.h b/keyboards/handwired/promethium/rgbsps.h
index 72612a7a82..77689344fc 100644
--- a/keyboards/handwired/promethium/rgbsps.h
+++ b/keyboards/handwired/promethium/rgbsps.h
@@ -1,3 +1,5 @@
+#pragma once
+
 void rgbsps_set(uint8_t index, uint8_t r, uint8_t g, uint8_t b);
 void rgbsps_setall(uint8_t r, uint8_t g, uint8_t b);
 void rgbsps_turnoff(void);
diff --git a/keyboards/handwired/symmetric70_proto/matrix_fast/test_config.h b/keyboards/handwired/symmetric70_proto/matrix_fast/test_config.h
index 25b5d4e018..bc9adddbbd 100644
--- a/keyboards/handwired/symmetric70_proto/matrix_fast/test_config.h
+++ b/keyboards/handwired/symmetric70_proto/matrix_fast/test_config.h
@@ -1,3 +1,5 @@
+#pragma once
+
 // list of OUTPUT(row) ports
 #define MATRIX_OUT_PORTS (Port_D, MCU_GPIO, D0), (Port_C, MCU_GPIO, C0), (Port_E, MCU_GPIO, E0), (Port_B, MCU_GPIO, B0)
 // list of OUTPUT(row) pins
diff --git a/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_74hc157.h b/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_74hc157.h
index 6abc25b862..bb310f28f9 100644
--- a/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_74hc157.h
+++ b/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_74hc157.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #define MATRIX_EXTENSION_74HC157 B2
 // #define MATRIX_EXTENSION_74HC153 B2, B6
 
diff --git a/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_direct.h b/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_direct.h
index aeea12950d..8b475ddcd6 100644
--- a/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_direct.h
+++ b/keyboards/handwired/symmetric70_proto/matrix_fast/test_config_direct.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #if defined(__AVR__)
 /* -------------------- AVR (Pro Micro) ----------------------- */
 
diff --git a/keyboards/hhkb/rn42/suart.h b/keyboards/hhkb/rn42/suart.h
index 7d92be0692..40e40648c7 100644
--- a/keyboards/hhkb/rn42/suart.h
+++ b/keyboards/hhkb/rn42/suart.h
@@ -1,8 +1,5 @@
-#ifndef SUART
-#define SUART
+#pragma once
 
 void xmit(uint8_t);
 uint8_t rcvr(void);
 uint8_t recv(void);
-
-#endif	/* SUART */
diff --git a/keyboards/horrortroll/handwired_k552/lib/bongocat.h b/keyboards/horrortroll/handwired_k552/lib/bongocat.h
index 65ceabc682..2ffeca1993 100644
--- a/keyboards/horrortroll/handwired_k552/lib/bongocat.h
+++ b/keyboards/horrortroll/handwired_k552/lib/bongocat.h
@@ -14,4 +14,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_bongocat(void);
diff --git a/keyboards/horrortroll/handwired_k552/lib/galaxy.h b/keyboards/horrortroll/handwired_k552/lib/galaxy.h
index 54ce2ad90a..3173278eff 100644
--- a/keyboards/horrortroll/handwired_k552/lib/galaxy.h
+++ b/keyboards/horrortroll/handwired_k552/lib/galaxy.h
@@ -14,4 +14,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_galaxy(void);
diff --git a/keyboards/horrortroll/handwired_k552/lib/logo.h b/keyboards/horrortroll/handwired_k552/lib/logo.h
index 5a917ae820..ba53e55476 100644
--- a/keyboards/horrortroll/handwired_k552/lib/logo.h
+++ b/keyboards/horrortroll/handwired_k552/lib/logo.h
@@ -14,4 +14,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_logo(void);
diff --git a/keyboards/horrortroll/lemon40/lib/bongocat.h b/keyboards/horrortroll/lemon40/lib/bongocat.h
index 65ceabc682..2ffeca1993 100644
--- a/keyboards/horrortroll/lemon40/lib/bongocat.h
+++ b/keyboards/horrortroll/lemon40/lib/bongocat.h
@@ -14,4 +14,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 void render_bongocat(void);
diff --git a/keyboards/marksard/rhymestone/common/oled_helper.h b/keyboards/marksard/rhymestone/common/oled_helper.h
index 34bacc6a89..9495937e2a 100644
--- a/keyboards/marksard/rhymestone/common/oled_helper.h
+++ b/keyboards/marksard/rhymestone/common/oled_helper.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #include <stdint.h>
 #include "action.h"
 
diff --git a/keyboards/marksard/treadstone48/common/oled_helper.h b/keyboards/marksard/treadstone48/common/oled_helper.h
index 82c1feba4a..3dc186f05c 100644
--- a/keyboards/marksard/treadstone48/common/oled_helper.h
+++ b/keyboards/marksard/treadstone48/common/oled_helper.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #ifdef OLED_ENABLE
 
 #include <stdint.h>
diff --git a/keyboards/work_louder/rgb_functions.h b/keyboards/work_louder/rgb_functions.h
index 8940cddefc..9ad7cdb19c 100644
--- a/keyboards/work_louder/rgb_functions.h
+++ b/keyboards/work_louder/rgb_functions.h
@@ -14,6 +14,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 #include "quantum.h"
 
 #ifndef VIA_ENABLE
diff --git a/keyboards/yushakobo/quick17/quick17_prefs.h b/keyboards/yushakobo/quick17/quick17_prefs.h
index a6096f0f26..25f2e1e0ae 100644
--- a/keyboards/yushakobo/quick17/quick17_prefs.h
+++ b/keyboards/yushakobo/quick17/quick17_prefs.h
@@ -14,6 +14,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 #include "quantum.h"
 
 enum layer_names {