'Lost in Space' Star June Lockhart Dead at 100

June Lockhart -- a legendary television actress of the 1950s, '60s and '70s -- has died.

Lockhart passed away Thursday in Santa Monica, just after 9 PM local time with her daughter June Elizabeth, and her granddaughter, Christianna, by her side, TMZ can confirm. June died from natural causes.

The daughter of actors Gene and Kathleen Lockhart, June secured her first credited role in the 1940 movie "All This, and Heaven Too" when she was still just a teenager.

June grabbed parts in iconic films like "Meet Me in St. Louis," "Sergeant York" and "T-Men" during the '40s before making the jump to television when the medium took off in the 1950s.

She secured her first big role in the "Lassie" TV show in 1958 when she took over the role of June Martin from Cloris Leachman ... a part she played in more than 200 episodes of the show, from '58 through '64.

After "Lassie", Lockhart appeared in a series of TV shows like "The Man From U.N.C.L.E" and "Bewitched" -- always in one episode bit parts.

Science fiction fans may recognize her as Dr. Maureen Robinson the biochemist in "Lost in Space" in all 84 episodes of the show.

Other shows include ... "Petticoat Junction," "The Beverly Hillbillies," "Vega$," "Murder, She Wrote," "Babylon 5," "Beverly Hills, 90210," "Johnny Bravo" and more. In her final role, she lent her voice to the part of Alpha Control in the "Lost in Space" reboot.

June has 2 stars on the Hollywood Walk of Fame -- one for TV and one for movies. She married twice, with both marriages ending in divorce.

Lockhart was 100.