Gerhard Peter Frantz Munthe (19 July 1849, Elverum, Hedmark – 15 January 1929) was a Norwegian painter and illustrator.
Munthe was born in Elverum to physician Christopher Pavels Munthe (1816–1884) and his wife Christine Margrethe Pavels Aabel (1827–1887). He was a brother of historian Hartvig Andreas Munthe, writer Margrethe Munthe and military officer Carl Oscar Munthe. He was also a nephew of historian and cartographer Gerhard Munthe and an uncle of genealogist Christopher Morgenstierne Munthe, librarian Wilhelm Munthe and painter Lagertha Munthe. Through his mother he was a nephew of Andreas Leigh Aabel and Oluf Andreas Aabel, and a first cousin of Hauk Aabel.
In December 1886 he married Sigrun Sandberg (1869–1957). Between 1886 and 1890 Bjørn Bjørnson was his stepfather-in-law. Munthe and Sandberg settled in Sandvika and later Lysaker. Also, Munthe had a studio at Ringstabekk for a short period. The couple divorced in 1919, the same year she married Fridtjof Nansen. Munthe was a prolific letter writer, and also published several articles, some of which were collected and published in 1919 as Minder og meninger. When Munthe moved to Christiania in 1863, his intention was to study medicine like his father, but his father advised him to take up the arts. He studied under Johan Fredrik Eckersberg in 1870, and continued under Morten Müller and Knud Bergslien until 1874.