John Ottis Adams was an American impressionist painter and art educator who is best known as a member of the Hoosier Group of Indiana landscape painters, along with William Forsyth, Richard B. Gruelle, Otto Stark, and T. C. Steele. In addition, Adams was among a group that formed the Society of Western Artists in 1896, and served as the organization's president in 1908 and 1909.

Adams grew up in central Indiana, but received his formal art training at the South Kensington School of Art in London. He spent seven years in Germany, where he attended the Academy of Fine Arts, Munich. Adams formed the Muncie Art School with Forsyth, but the school closed after two years. Adams also assisted in planning and taught art classes at the John Herron Art Institute, which later became the Indianapolis Museum of Art and the John Herron School of Art in Indianapolis. He also gave informal art lessons at the Hermitage, his home and studio near Brookville, Indiana. In 2004 the building was listed on the National Register of Historic Places; it is also a contributing property to the Brookville Historic District.

Several major exhibitions have included Adams's work: Five Hoosier Painters in Chicago, Illinois, in 1894; the Louisiana Purchase Exposition (World's Fair) in Saint Louis, Missouri, in 1904; the Panama–Pacific International Exposition in San Francisco, California, in 1915; and the first Hoosier Salon in Chicago in 1925. In 1910 Adams exhibited internationally at the Buenos Aires Exposition in Buenos Aires, Argentina and Santiago, Chile, where one of his paintings, A Frosty Morning, received an honorable mention. Adams won several other prizes for his art. Iridescence of a Shallow Stream won a bronze medal at the Louisiana Purchase Exposition (the 1904 World's Fair) and A Winter Morning won the $500 Fine Arts Building Prize at the Society of Western Artists exhibition in Chicago in 1907. Adams's work is represented in the collections of several Indiana civic and cultural institutions.

Today his paintings are held in a number of private collections and museums, including the Haan Mansion Museum of Indiana Art.