diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -293,6 +293,17 @@
 TUNABLE_STR("hw.acpi.remove_interface", acpi_remove_interface,
     sizeof(acpi_remove_interface));
 
+/*
+ * Automatically apply the Darwin OSI on Apple Mac hardware to obtain
+ * access to full ACPI hardware support on supported platforms.
+ *
+ * This flag automatically overrides any values set by
+ * `hw.acpi.acpi_install_interface` and unset by
+ * `hw.acpi.acpi_remove_interface`.
+ */
+static int acpi_apple_darwin_osi = 1;
+TUNABLE_INT("hw.acpi.apple_darwin_osi", &acpi_apple_darwin_osi);
+
 /* Allow users to dump Debug objects without ACPI debugger. */
 static int acpi_debug_objects;
 TUNABLE_INT("debug.acpi.enable_debug_objects", &acpi_debug_objects);
@@ -4903,6 +4914,67 @@
 		}
 		acpi_free_interfaces(&list);
 	}
+
+	/*
+	 * Apple Mac hardware quirk: install Darwin OSI.
+	 *
+	 * On Apple hardware, install the Darwin OSI and remove the Windows OSI
+	 * to match Linux behavior.
+	 *
+	 * This is required for dual-GPU MacBook Pro systems
+	 * (Intel iGPU + AMD/NVIDIA dGPU) where the iGPU is hidden when the
+	 * firmware doesn't see Darwin OSI, but it also unlocks additional ACPI
+	 * support on non-MacBook Pro Apple platforms.
+	 *
+	 * Apple's ACPI firmware checks _OSI("Darwin") and sets OSYS=10000
+	 * for macOS. Many device methods use OSDW() which checks OSYS==10000
+	 * for macOS-specific behavior including GPU visibility and power
+	 * management.
+	 *
+	 * Linux enables Darwin OSI by default on Apple hardware and disables
+	 * all Windows OSI strings (drivers/acpi/osi.c). Users can override
+	 * this behavior with acpi_osi=!Darwin to get Windows-like behavior,
+	 * in general, but this logic makes that process unnecessary.
+	 *
+	 * Detect Apple via SMBIOS and enable Darwin while disabling Windows
+	 * vendor strings. This makes both GPUs visible on dual-GPU MacBook Pro
+	 * systems (Intel iGPU + AMD dGPU) and unlocks full platform
+	 * ACPI support.
+	 */
+	if (acpi_apple_darwin_osi) {
+		char *vendor = kern_getenv("smbios.system.maker");
+		if (vendor != NULL) {
+			if (strcmp(vendor, "Apple Inc.") == 0 ||
+			    strcmp(vendor, "Apple Computer, Inc.") == 0) {
+				/* Disable all other OSI vendor strings. */
+				status = AcpiUpdateInterfaces(
+				    ACPI_DISABLE_ALL_VENDOR_STRINGS);
+				/* Install Darwin */
+				if (ACPI_SUCCESS(status)) {
+					status = AcpiInstallInterface("Darwin");
+				}
+				if (bootverbose) {
+					if (ACPI_SUCCESS(status)) {
+						device_printf(dev,
+						    "Apple hardware: installed Darwin "
+						    "OSI and removed other vendor OSI "
+						    "(Windows, etc)\n");
+					} else {
+						device_printf(dev,
+						    "Apple hardware: failed to install "
+						    "Darwin OSI: %s\n",
+						    AcpiFormatException(
+							status));
+					}
+				}
+			} else if (bootverbose) {
+				device_printf(dev,
+				    "Not installing Darwin OSI on unsupported platform: %s\n",
+				    vendor);
+			}
+			freeenv(vendor);
+		}
+	}
 }
 
 static int