OSCAR-WINNING Australian actress Cate Blanchett has given birth to her third child in Sydney, a spokesman said yesterday.

Blanchett and her playwright husband Andrew Upton welcomed Ignatius Martin Upton into the world Sunday, a spokesman for the Sydney Theater Co. said.

"The baby was born yesterday. Both are doing well," he said yesterday.

Blanchett and Upton, joint artistic directors of the theater company, already have two sons: Dashiell John, aged 6, and Roman Robert, aged 3.

The "Elizabeth: The Golden Age" and "I'm Not There" star's latest boy weighed 3.6kg, media reports said.

Blanchett missed out on a second Oscar at this year's ceremony, losing to Tilda Swinton and Marion Cotillard in two female acting categories.

She is shortly to star alongside Harrison Ford as Agent Irina Spalko in the fourth installment of the Indiana Jones series, titled "Indiana Jones and the Kingdom of the Crystal Skull."

Blanchett has been picked by Australian Prime Minister Kevin Rudd to head a think-tank on the future of arts in her home country this weekend as past of a summit on challenges facing Australia, leading 100 of the country's best minds.

(SD-Agencies)