With partner Joseph Barbera, built an animation empire, creating such classic cartoons as Tom & Jerry, Scooby-Doo, Yogi Bear, the Jetsons, the Flintstones, Jonny Quest, the Smurfs, and many, many others.
In 1930, began working at the Harman-Ising cartoon studios, providing story ideas, music and lyrics for the Looney Tunes and Merrie Melodies series, and becoming an MGM story editor and director when Harman-Ising moved to that studio.
In 1937, MGM formed its own animation department led by Fred Quimby, who hired Hanna and teamed him with Barbera.
Melded animation with live-action films, such as when Jerry the mouse danced with Gene Kelly in Anchors Aweigh (1945) and swam with both cartoon co-star Tom and aquatic actress Esther Williams in Dangerous When Wet (1953).
Earned multiple Oscar awards and nominations, prompting a promotion to head of MGM's animation department; when that department was shuttered in 1957, Barbera and Hanna were free to build their company, Hanna-Barbera Productions, for animated TV series.
Developed a production technique called "limited animation" that made cartoons more efficient to produce on a larger scale, thereby facilitating the creation of their weekly series.
His Emmy-winning cartoon The Last of the Curlews (1972) became the first ABC Afterschool Special.