Walter D. "Spec" O'Donnell (April 9, 1911 – October 14, 1986) was an American film actor who appeared in more than 190 films between 1923 and 1978.

He worked frequently for producer Hal Roach, often appearing in silent comedies as the bratty son of Max Davidson or Charley Chase. His sound-era roles were mostly uncredited bits, often as bellhops, newsboys, and pages; he was playing adolescent roles well into his twenties. He has the unusual distinction of playing the same role (a newsboy) in both an original film and its remake: Princess O'Hara and It Ain't Hay.

O'Donnell was born in Madera, California. His father, John O'Donnell, was a lumber mill labourer originally from Maryland. His mother and older siblings (Jack and Minnie) were born in California.

In February 1924, O'Donnell signed with Julius and Abe Stern's Century Film Corporation.

In 1924, O'Donnell starred in Walt Disney's Alice Comedies. The first of these was Alice's Spooky Adventure, where he features as one of several children playing baseball in a field. The film also starred Virginia Davis (as Alice) and Leon Holmes, with whom O'Donnell featured alongside in Alice the Peacemaker during the same year. He also had parts in Alice Gets in Dutch and Alice is Stage Struck, which was released the following year.

O'Donnell died in 1986 in Woodland Hills, Los Angeles.