Nancy Beaumont, the mother of the three missing Beaumont children, has died in Adelaide aged 92.

Mrs Beaumont passed away on Monday in a nursing home and her death was confirmed in a notice published on Thursday.

The Beaumont children Arnna, Grant and Jane. Credit:Fairfax Media

The disappearance of her three children – Jane, 9, Arnna, 7, and Grant, 4 – on Australia Day in 1966 is one of the country's most enduring mysteries.

The children never returned after leaving their parents' home for an afternoon at Glenelg Beach. There was an intense search but they were never found.