Robert Edward Barthelson (July 15, 1924 – April 14, 2000) was a Major League Baseball pitcher who played for the New York Giants in 1944. The 6 ft 0 in (1.83 m), 185 lb (84 kg) right-hander graduated from Hillhouse High School.^[1]

Barthelson is one of many ballplayers who only appeared in the major leagues during World War II. At the age of 19 he made his major league debut in a 4 July doubleheader against the St. Louis Cardinals at Sportsman's Park. Three weeks later, in his only big league start, he lost to the Pittsburgh Pirates at the Polo Grounds.

In a total of seven games he was 1–1 with 5 games finished, allowing 5 earned runs in 92⁄3 innings pitched for a final ERA of 4.66.^[2]

After his brief major league career ended, Barthelson became a pitcher for the West Haven Sailors,^[1] an independent semiprofessional team in West Haven, Connecticut, that scheduled games against Negro leagues and major league teams.^[3] He also pitched for the San Francisco Seals in 1945, for the Minneapolis Millers in 1946, and for the Sacramento Solons in 1947.^[2][4]

Barthelson died in 2000 in Branford, Connecticut.^[5]