Onni Alfred Muusari was a Finnish illustrator and painter.

Muusari studied at the Drawing School of the Friends of Art in Vyborg in 1906–1908 and 1910 and at the School of Drawing of the Finnish Art Association in 1909. He participated in exhibitions by Finnish artists in 1912, 1913 and 1914. Muusari worked as a cartoonist, illustrator and book cover designer.