Peter Fagg (January 14, 1837 – December 10, 1917) was an American law enforcement officer, retail clerk, debt collector, temperance lecturer, colporteur, and politician from Milwaukee and Madison, Wisconsin who served a single term as a member of the Wisconsin State Assembly's 2nd Milwaukee County district (the 2nd Ward of the City of Milwaukee). He was a member of the Reform Party, a short-lived coalition of Democrats, reform and Liberal Republicans, and Grangers formed in 1873 in the U.S. state of Wisconsin, which had secured the election for two years of William Robert Taylor as Governor of Wisconsin, as well as electing a number of state legislators, but failed to thrive.