|Date of birth:||December 4, 1899|
|Place of birth:||Llewellyn, Pennsylvania, United States|
|Date of death:||March 9, 1968(aged 68)|
|Place of death:||Williamsport, Pennsylvania, United States|
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John Oliver Ernst (December 4, 1899 – March 9, 1968) was an American football running back. He played six seasons for the Pottsville Maroons, New York Yankees, Boston Bulldogs, and Frankford Yellow Jackets. In 1925 Jack helped the Maroons win the NFL Championship, before it was stripped from the team due to a disputed rules violation.