June Lockhart, the beloved American actress whose warmth and poise defined classic television hits like "Lost in Space" and "Lassie", has died of natural causes at her home in Santa Monica, California. She was 100.

Born in New York City in 1925 to actors Gene and Kathleen Lockhart, she seemed destined for the screen. At just 13, she made her film debut alongside her parents in Edwin L Marin's 1939 adaptation of "A Christmas Carol", playing Belinda Cratchit. Her early success led to roles in films such as "All This, and Heaven Too", "Meet Me in St Louis", "The Yearling", and "Sergeant York."

Lockhart rose to national prominence in the late 1950s as Ruth Martin, Timmy's foster mother, in the CBS family drama "Lassie." She played the role from 1958 to 1964, succeeding Cloris Leachman and helping cement the show's place in American pop culture.

Her next defining role came in 1965, when she joined another CBS hit — the sci-fi adventure "Lost in Space." Dr Maureen Robinson, the ship's resident biochemist and devoted mother, became a symbol of both maternal strength and quiet intelligence for an entire generation of viewers.

In a 2024 interview with Closer magazine, Lockhart reflected on her television years with fondness. "When I wasn't shooting 'Lassie', I became the mistress of Scrabble with my hairdresser and the crew," she said. "But 'Lost in Space' was my favourite — it was so campy, and I truly enjoyed my relationship with my space family."

Over a career that spanned nearly eight decades, Lockhart remained a constant presence on both the big and small screens. Her television credits included recurring roles in "Petticoat Junction", "General Hospital", and "Beverly Hills, 90210", along with guest appearances in "The Beverly Hillbillies", "Happy Days", "Full House", "Roseanne", and "Grey's Anatomy".

Before her television fame, she had appeared in the feature "Son of Lassie", and throughout the 1950s, she made her mark in Westerns such as "Wagon Train", "Cimarron City", "Gunsmoke", "Have Gun – Will Travel", and "Rawhide".

Lockhart earned two Emmy nominations, including Best Actress in a Leading Role for her performance in "Lassie." In 1948, she received a Special Tony Award for Outstanding Performance by a Newcomer for her Broadway role in "For Love or Money." Her contributions were later immortalised with two stars on the Hollywood Walk of Fame — one for film and one for television.

A private memorial service will be held in her honour. Her family has requested that, instead of flowers, donations be made to The Actors Fund, ProPublica, or International Hearing Dog, Inc.

FP/MI