Harold Charles Ostertag (June 22, 1896 – May 2, 1985) was an American politician, a United States Representative for the 41st, 39th, and 37th Congressional Districts of New York.
Ostertag was born on June 22, 1896, in Attica, New York, attended the public schools, and graduated from Chamberlain Military Institute in Perry, New York in 1915. He worked for the New York Central Railroad from 1917 to 1950, and became assistant to the vice president of the traffic department.
During World War I, Ostertag enlisted in the New York Army National Guard's 74th Infantry Regiment. This organization was federalized as the 55th Pioneer Infantry Regiment, a unit of the 27th Division. Ostertag, who had attained the rank of Sergeant, completed officer training and received his commission as a Second Lieutenant while serving with the 55th in France. After the war he was active in the American Legion and Veterans of Foreign Wars, and entered politics as a Republican.
Ostertag was a member of the New York State Assembly (Wyoming Co.) in 1932, 1933, 1934, 1935, 1936, 1937, 1938, 1939–40, 1941–42, 1943–44, 1945–46, 1947–48 and 1949–50.
He was elected as a Republican to the 82nd, 83rd, 84th, 85th, 86th, 87th and 88th United States Congresses, holding office from January 3, 1951, to January 3, 1965. He did not run for re-election in 1964.
Ostertag was a delegate to the 1952, 1956 and 1960 Republican National Conventions.
Ostertag was a resident of Perry until he died in Pompano Beach, Florida, on May 2, 1985. He was interred at Forest Hill Cemetery in Attica.
Ostertag's wife Grace was Grand Matron of the Order of the Eastern Star and first vice president of the Congressional Club.