Charles Luman Knapp (July 4, 1847 – January 3, 1929) was an American politician from New York.

Then he studied law, was admitted to the bar in 1873, and practiced in Lowville.

He was appointed by President Benjamin Harrison as consul general at Montreal in 1889, and remained on the post until September 1893, when he returned to Lowville and resumed the practice of law.

Knapp was elected as a Republican to the 57th Congress to fill the vacancy caused by the death of Albert D. Shaw, and was re-elected to the 58th, 59th, 60th and 61st United States Congresses, holding office from November 5, 1901, to March 3, 1911.

He resumed the practice of law in Lowville, died there on January 3, 1929, and was buried at the Lowville Rural Cemetery.