Lagertha Munthe (16 March 1888 – 25 March 1984) was a Norwegian painter. She was born in Kristiania as a daughter of Olaf Andreas Jens Wilhelm Munthe (1851–1914). She was a grandniece of historian and cartographer Gerhard Munthe, a niece of historian Hartvig Andreas Munthe, painter Gerhard Munthe, writer Margrethe Munthe and Major General Carl Oscar Munthe, and a first cousin of librarian Wilhelm Munthe and genealogist Christopher Morgenstierne Munthe.