Gregory was born on the 4th of December, 1912 in Coeur d'Alene, Idaho and at the age of three, his family moved to St. Maries until he was twelve when they would move to Tacoma, Washington. Here he attended Lincoln High School and graduated in 1930. Gregory then attended the University of Washington in Seattle and was a member of the Army ROTC. He also wrestled, like he did in high school, and was a part of the swimming team. During the Summers, Gregory went to work in mining and logging camps as well as road construction. In 1934, he graduated with a BS in aeronautical engineering and got married soon after. He then worked as a draftsman and engineer for Boeing in Seattle.

Gregory applied for flight training in Spring of 1935 under the Aviation Cadet Act but found out that married men could not participate. At this time, Gregory had the last name of Hallenbeck and had grown up with that name. He assumed that his stepfather was his biological father and once he obtained his birth certificate, he learned that his biological father and his mother were divorced when he was an infant. Since there was no record of a Gregory Boyington ever being married, he enrolled in the US Marine Corps aviation cadet program with that name.

During his time in the Army ROTC, Gregory had become a cadet captain and had been commissioned as a second lieutenant in the US Army Coast Artillery Reserve just after college. He served two months of active duty at Fort Worden in Washington with the 630th Coast Artillery and later transferred to the US Marine Corps Reserve in June of 1935. The 18th of February, 1936 is when Gregory accepted an appointment to the aviation cadet program and was assigned to Naval Air Station in Pensacola, Florida for flight training. He received his Naval Aviator designation on the 11th of March, 1937 and was transferred to Quantico, Virginia for duty with Aircraft One, Fleet Marine Force. Gregory accepted a second lieutenant's commission in the active Marine Corps on the 2nd of July and then attended The Basic School in Philadelphia the following year. With the 2nd Marine Aircraft Group, Gregory spent time on the USS Lexington and USS Yorktown and was promoted to first lieutenant on the 4th of November, 1940 before returning to Pensacola as an instructor the following month.

In August of 1941, Gregory resigned his commission in order to accept a position with Central Aircraft Manufacturing Company, or CAMCO. This was a civilian firm that staffed a Special Air Unit that would later be known as the American Volunteer Group. Their mission was to defend China and the Burma Road and Gregory became a flight leader of the Flying Tigers. After about eight months, he broke his contract and returned to the States and he rejoined the Marine Corps five months later on the 29th of September, 1942. At this time, the Marine Corps needed experience combat pilots and now a Major, Gregory was assigned to Marine Aircraft Group 11 of the 1st Marine Aircraft Wing. He was deployed to the South Pacific with Marine Fighter Squadron 122 as their executive officer on Guadalcanal. He then became the commander of Marne Fighter Squadron 112 before becoming the commanding officer of Marine Fighter Squadron 214 in September of 1943. VMF-214 was better known as the “Black Sheep Squadron” and Gregory had now earned the nickname of “Gramps” and eventually “Pappy”, due to being a decade older than most of the Marines serving under him.

Gregory was shot down on the 3rd of January but it was his actions leading up to this attack that would earn him the Medal of Honor. The citation reads:

For extraordinary heroism above and beyond the call of duty as Commanding Officer of Marine Fighting Squadron TWO FOURTEEN in action against enemy Japanese forces in Central Solomons Area from September 12, 1943 to January 3, 1944. Consistently outnumbered throughout successive hazardous flights over heavily defended hostile territory, Major Boyington struck at the enemy with daring and courageous persistence, leading his squadron into combat with devastating results to Japanese shipping, shore installations and aerial forces. Resolute in his efforts to inflict crippling damage on the enemy, Major BOYINGTON led a formation of twenty-four fighters over Kahili on October 17, and, persistently circling the airdrome where sixty hostile aircraft were grounded, boldly challenged the Japanese to send up planes. Under his brilliant command, our fighters shot down twenty enemy craft in the ensuing action without the loss of a single ship. A superb airman and determined fighter against overwhelming odds, Major BOYINGTON personally destroyed 26 of the many Japanese planes shot down by his squadron and by his forceful leadership developed the combat readiness in his command which was a distinctive factor in the Allied aerial achievements in this vitally strategic area.

On the 3rd of January, 1944, Gregory had tied World War 1 ace Eddie Rickenbacker's record for destroyed enemy planes of 26. He later claimed his total was 28, which included the six kills he had during his time with the Flying Tigers. On that day, forty-eight American fighters were sent on a mission over Rabaul and shortly after being seen shoot down his 26th plane, Gregory's plane became mixed up in a dogfight and wasn't seen during the rest of the battle and did not return with the squadron. His wingman, George Ashmun, was killed during this action as well. Gregory was deemed missing in action after a search, mostly because he had been picked up by a Japanese submarine and became a prisoner of war, although the Japanese never gave him official POW status and never reported his captivity to the Red Cross. He spent the next 20 months in several Japanese prisoner camps until the 29th of August 1945 when the atomic bombs were dropped and the Japanese capitulated.

Gregory was liberated from Omori Prison Camp and returned to Naval Air Station Alameda on the 12th of September, 1945. He was greeted by 21 former members VMF-214 and that night a party was held at the St Francis Hotel in San Francisco. The party was covered by Life Magazine for its October 1945 issue and it was the first time the magazine had ever shown people consuming alcohol. About a month later, Gregory, now a Lieutenant Colonel, received the Navy Cross for his actions during the Rabaul raid and the next day, the 5th of October 1945, he received the Medal of Honor from President Truman. His Medal had actually been awarded to him in March of 1944 by President Roosevelt but was being held for a time that he could actually receive it. After his Victory Bond tour and a few other assignments, Gregory retired from the Marine Corps on the 1stof August 1947 and was promoted to Colonel because of his performance of duty in combat.

Gregory was a heavy smoker and drinker and through four marriages, he managed to write his autobiography, Baa Baa Black Sheep, in 1958 and it would later serve as a very loose base for the 1970s television show of the same name. Gregory would later be inducted into the Naval Aviation Hall of Honor in 1994 and the airport in his home town was renamed to the Coeur d'Alene Airport-Pappy Boyington Field in August of 2007. After much debate, the University of Washington scrapped a project to memorialize just Gregory and on Veterans Day in 2009 a memorial to Gregory and seven other Medal of Honor recipients that were alumni was completed. Gregory H Boyington died on the 11thof January, 1988 at the age of 75 after battling cancer since the 1960s. He was buried in Arlington National Cemetery on the 15th of January in section 7A, site 150 and the F-4 VMA-214 (the modern version of the Black Sheep Squadron) did a flyby during the ceremony. He is buried adjacent to boxing legend Joe Louis and film star Lee Marvin.