John Greig (August 6, 1779 – April 9, 1858) was an American lawyer and politician who served briefly as a United States representative from New York in 1841.

Greig was born in Moffat, Dumfriesshire, Scotland in the Kingdom of Great Britain on August 6, 1779, and attended the Edinburgh High School.

He immigrated to the United States in 1797, studied law; was admitted to the bar and commenced practice in Canandaigua, New York.

He served as president of the Ontario Bank, was president of the Ontario Agricultural Society, and was a member and vice chancellor of the Board of Regents for the University of the State of New York.

He died in Canandaigua on April 9, 1858, with interment in West Avenue Cemetery.