diff --git a/docs/mmio.md b/docs/mmio.md
index 49542f3..4ee6f80 100644
--- a/docs/mmio.md
+++ b/docs/mmio.md
@@ -12,10 +12,12 @@ mmio_t *mmio_new(void);
 int mmio_open(mmio_t *mmio, uintptr_t base, size_t size);
 int mmio_open_advanced(mmio_t *mmio, uintptr_t base, size_t size, const char *path);
 void *mmio_ptr(mmio_t *mmio);
+int mmio_read64(mmio_t *mmio, uintptr_t offset, uint64_t *value);
 int mmio_read32(mmio_t *mmio, uintptr_t offset, uint32_t *value);
 int mmio_read16(mmio_t *mmio, uintptr_t offset, uint16_t *value);
 int mmio_read8(mmio_t *mmio, uintptr_t offset, uint8_t *value);
 int mmio_read(mmio_t *mmio, uintptr_t offset, uint8_t *buf, size_t len);
+int mmio_write64(mmio_t *mmio, uintptr_t offset, uint64_t value);
 int mmio_write32(mmio_t *mmio, uintptr_t offset, uint32_t value);
 int mmio_write16(mmio_t *mmio, uintptr_t offset, uint16_t value);
 int mmio_write8(mmio_t *mmio, uintptr_t offset, uint8_t value);
@@ -76,12 +78,13 @@ This function is a simple accessor to the MMIO handle structure and always succe
 ------
 
 ``` c
+int mmio_read64(mmio_t *mmio, uintptr_t offset, uint64_t *value);
 int mmio_read32(mmio_t *mmio, uintptr_t offset, uint32_t *value);
 int mmio_read16(mmio_t *mmio, uintptr_t offset, uint16_t *value);
 int mmio_read8(mmio_t *mmio, uintptr_t offset, uint8_t *value);
 int mmio_read(mmio_t *mmio, uintptr_t offset, uint8_t *buf, size_t len);
 ```
-Read 32-bits, 16-bits, 8-bits, or an array of bytes, respectively, from mapped physical memory, starting at the specified byte offset, relative to the base address the MMIO handle was opened with.
+Read 64-bits, 32-bits, 16-bits, 8-bits, or an array of bytes, respectively, from mapped physical memory, starting at the specified byte offset, relative to the base address the MMIO handle was opened with.
 
 `mmio` should be a valid pointer to an MMIO handle opened with one of the `mmio_open*()` functions.
 
@@ -90,12 +93,13 @@ Returns 0 on success, or a negative [MMIO error code](#return-value) on failure.
 ------
 
 ``` c
+int mmio_write32(mmio_t *mmio, uintptr_t offset, uint64_t value);
 int mmio_write32(mmio_t *mmio, uintptr_t offset, uint32_t value);
 int mmio_write16(mmio_t *mmio, uintptr_t offset, uint16_t value);
 int mmio_write8(mmio_t *mmio, uintptr_t offset, uint8_t value);
 int mmio_write(mmio_t *mmio, uintptr_t offset, const uint8_t *buf, size_t len);
 ```
-Write 32-bits, 16-bits, 8-bits, or an array of bytes, respectively, to mapped physical memory, starting at the specified byte offset, relative to the base address the MMIO handle was opened with.
+Write 64-bits, 32-bits, 16-bits, 8-bits, or an array of bytes, respectively, to mapped physical memory, starting at the specified byte offset, relative to the base address the MMIO handle was opened with.
 
 `mmio` should be a valid pointer to an MMIO handle opened with one of the `mmio_open*()` functions.
 
diff --git a/src/mmio.c b/src/mmio.c
index 8f2fae7..04e8e7c 100644
--- a/src/mmio.c
+++ b/src/mmio.c
@@ -98,6 +98,15 @@ void *mmio_ptr(mmio_t *mmio) {
 /* WARNING: These functions may trigger a bus fault on some CPUs if an
  * unaligned address is accessed! */
 
+int mmio_read64(mmio_t *mmio, uintptr_t offset, uint64_t *value) {
+    offset += (mmio->base - mmio->aligned_base);
+    if ((offset+8) > mmio->aligned_size)
+        return _mmio_error(mmio, MMIO_ERROR_ARG, 0, "Offset out of bounds");
+
+    *value = *(volatile uint64_t *)(((volatile uint8_t *)mmio->ptr) + offset);
+    return 0;
+}
+
 int mmio_read32(mmio_t *mmio, uintptr_t offset, uint32_t *value) {
     offset += (mmio->base - mmio->aligned_base);
     if ((offset+4) > mmio->aligned_size)
@@ -134,6 +143,15 @@ int mmio_read(mmio_t *mmio, uintptr_t offset, uint8_t *buf, size_t len) {
     return 0;
 }
 
+int mmio_write64(mmio_t *mmio, uintptr_t offset, uint64_t value) {
+    offset += (mmio->base - mmio->aligned_base);
+    if ((offset+8) > mmio->aligned_size)
+        return _mmio_error(mmio, MMIO_ERROR_ARG, 0, "Offset out of bounds");
+
+    *(volatile uint64_t *)(((volatile uint8_t *)mmio->ptr) + offset) = value;
+    return 0;
+}
+
 int mmio_write32(mmio_t *mmio, uintptr_t offset, uint32_t value) {
     offset += (mmio->base - mmio->aligned_base);
     if ((offset+4) > mmio->aligned_size)
diff --git a/src/mmio.h b/src/mmio.h
index 64be152..deaae80 100644
--- a/src/mmio.h
+++ b/src/mmio.h
@@ -28,10 +28,12 @@ mmio_t *mmio_new(void);
 int mmio_open(mmio_t *mmio, uintptr_t base, size_t size);
 int mmio_open_advanced(mmio_t *mmio, uintptr_t base, size_t size, const char *path);
 void *mmio_ptr(mmio_t *mmio);
+int mmio_read64(mmio_t *mmio, uintptr_t offset, uint64_t *value);
 int mmio_read32(mmio_t *mmio, uintptr_t offset, uint32_t *value);
 int mmio_read16(mmio_t *mmio, uintptr_t offset, uint16_t *value);
 int mmio_read8(mmio_t *mmio, uintptr_t offset, uint8_t *value);
 int mmio_read(mmio_t *mmio, uintptr_t offset, uint8_t *buf, size_t len);
+int mmio_write64(mmio_t *mmio, uintptr_t offset, uint64_t value);
 int mmio_write32(mmio_t *mmio, uintptr_t offset, uint32_t value);
 int mmio_write16(mmio_t *mmio, uintptr_t offset, uint16_t value);
 int mmio_write8(mmio_t *mmio, uintptr_t offset, uint8_t value);