Hajime Sugiyama (杉山 元, Sugiyama Hajime / Sugiyama Gen; 1 January 1880 – 12 September 1945) was a Japanese field marshal and one of Japan's military leaders for most of the Second World War.

As Army Minister, Sugiyama was a driving force behind Japan's 1937 invasion of China in retaliation for the Marco Polo Bridge Incident. After being named the Japanese Army's Chief of Staff in 1940, he became a leading advocate for expansion into Southeast Asia and preventive war against the United States.

Upon the outbreak of hostilities in the Asia-Pacific theater of World War II, Sugiyama served as the army's de facto commander-in-chief until his removal by Prime Minister Hideki Tojo in February 1944. Following Tojo's ouster in July 1944, he once again held the post of Army Minister in Kuniaki Koiso's cabinet until its dissolution in April 1945. Ten days after Japan's surrender on 2 September 1945, he committed suicide.

Born to a former samurai family from Kokura (now part of Kitakyushu City), Fukuoka Prefecture, Sugiyama graduated from the 12th class of the Imperial Japanese Army Academy in 1901. He served as a junior officer with 3rd Battalion of the 14th Regiment of the IJA 12th Division in the Russo-Japanese War, and was wounded in the face during the Battle of Shaho. Due to scars from that injury, he was unable to fully open his right eye.

After graduating from the 22nd class of the Army Staff College in 1910, Sugiyama served in Section 2 (Intelligence) within the Imperial Japanese Army General Staff. He was posted as military attaché to the Philippines and Singapore in 1912, disguised as a civilian trading company employee, and disguised as an Imperial Japanese Navy lieutenant, joined in an inspection tour of the United States Navy base at Subic Bay. Promoted to major in 1913, he was posted again as military attaché to British India in 1915, where he met in secret with Indian independence activists Rash Behari Bose and Subhas Chandra Bose. In 1918, he was sent as a military observer to the Middle Eastern theatre of World War I. At the end of the war, he served on the League of Nations committee on military aviation.

On his return to Japan, Sugiyama was promoted to lieutenant colonel, and commander of the 2nd Air Battalion in December 1918. Three years later in 1921, he was promoted to colonel. A strong proponent of military aviation, he ultimately rose to become the first head of the Imperial Japanese Army Air Service in 1922.

In 1924, Sugiyama became a protege of Army Minister Ugaki Kazushige. ^{[citation needed]} Subsequently, he was promoted to major general in May 1925 and appointed Director of the Bureau of Military Affairs in 1928. Within the same timeframe, he also became a leading figure in the Army's Control Faction, the Tōseiha.

In 1931, he participated in the March incident, a failed coup-d'etat which attempted to make Ugaki Prime Minister. Later that year, as Under Secretary of the Army, he made an official announcement defending the actions of the military in the Mukden Incident.^{[citation needed]}