John Newcomer (December 18, 1797 – April 21, 1861) was an American politician and farmer from Maryland. He served as a member of the Maryland Senate, representing Washington County, from 1840 to 1846.

John Newcomer was born on December 18, 1797, to Henry Newcomer.^[1]

Newcomer was a large real estate holder in Washington County, Maryland. He worked his farm and operated a mill in Beaver Creek. He founded Newcomer & Stonebraker, a flour and grain commission firm in Baltimore.^[1]

Newcomer served as sheriff of Washington County from 1836 to 1839.^[1][2] He served as a member of the Maryland Senate, representing Washington County, from 1840 to 1846.^[1][3] He served as county commissioner of Washington County in 1846 and 1859. He was a delegate to the convention that framed the Maryland Constitution of 1850.^[1]

Newcomer married his cousin Catherine Newcomer, daughter of Samuel Newcomer. Their son was Benjamin Franklin Newcomer.^[1]

Newcomer died on April 21, 1861.^[1][4]