Robert James Walker, Sr. was a senior sailor in the United States Navy who served as the third Master Chief Petty Officer of the Navy. He was born in Baldwin, New York, and attended grammar and high school in Oxford, New York.

The master chief petty officer of the Navy is a unique non-commissioned rank and position of office of the United States Navy, which is designated as a special paygrade above E-9. The holder of this position is the most senior enlisted member of the U.S. Navy, equivalent to the sergeant Major of the Army, chief master sergeant of the Air Force, sergeant major of the Marine Corps, master chief petty officer of the Coast Guard, and chief master sergeant of the Space Force. The holder of this rank and position is the most senior enlisted sailor in the Navy, unless an enlisted sailor is serving as the senior enlisted advisor to the chairman. The current MCPON is James Honea.