Joseph Morrill Harper (June 21, 1787 – January 15, 1865) was an American physician, banker and Jacksonian politician in the U.S. state of New Hampshire.

Harper was born in Limerick (in modern-day Maine, then a part of Massachusetts) and attended Fryeburg Academy.

[4] He was a member of the New Hampshire House of Representatives in 1826 and 1827, and justice of the peace in Canterbury from 1826 to 1865.

Harper served as Acting Governor from February 1831 – June 1831.

[8] Harper died on January 15, 1865, in Canterbury,[9] and is interred in the Village Cemetery.