Erwin Arthur Renfer (December 11, 1891 – October 26, 1957) was an American baseball pitcher from 1910 to 1915. He compiled a 61–35 record in 131 minor league games,^[1] and he also appeared in one game in Major League Baseball for the Detroit Tigers in September 1913.^[2]

Renfer was born in Elgin, Illinois, in 1891 and attended Virginia Polytechnic Institute and State University (Virginia Tech).^[2] In October 1910, at age 18, he was included on the reserve list of the Detroit Tigers.^[3] In May 1911, the Tigers assigned Renfer to play with the Saginaw club in the Southern Michigan League.^[4] At age 19, Renfer appeared in 34 games and compiled a 15–10 record for Saginaw during the 1911 season.^[1] In January 1912, Frank Navin, president of the Detroit Tigers, announced that the team had given Renfer his outright release.^[5]

Renfer spent most of the 1912 and 1913 seasons playing for the Ottawa Senators in the Canadian League. He appeared in 52 games for Ottawa, compiling a 34–10 record in 1912 and 1913.^[1] He also appeared in six Central League games for the Fort Wayne Railroaders during the 1912 season.^[1]

At the end of August 1913, Renfer was purchased by the Detroit Tigers.^[6] In his sole appearance in Major League Baseball, on September 18, 1913, Renfer pitched six innings and gave up four earned runs for a career earned run average of 6.00.^[2]

After his short stint with the Detroit Tigers, Renfer played two seasons in the Southern Association. In 1914, he appeared in 31 games for the Nashville Volunteers and compiled a 9–11 record. He concluded his professional baseball career in 1915 with the Memphis Chickasaws, compiling a 2–2 record in eight games.^[1]

Renfer died in Sycamore, Illinois, in 1957 at age 65.^[2] He was buried at the Bluff City Cemetery in Elgin, Illinois.^[7]