Zoo authorities in the Indian capital Delhi are holding a party to celebrate the 57th birthday of Rita the chimpanzee, its oldest resident.
The "birthday girl" will get presents and a cake will be cut in her honour, Zoo director Renu Singh told the BBC.
India's oldest living chimpanzee was born in Amsterdam in 1960 and arrived at Delhi zoo as a four-year-old.
She's a "very friendly" ape, Ms Singh said. "We will cut a cake and I'll feed a big slice to Rita with my hands."
Schoolchildren will join Thursday's celebrations - the party is being held a day early because Rita's birthday falls on a day when the zoo is closed.Her presents will include a soft football and other toys, as well as a new blanket.
"We will also screen some wildlife films for her as a birthday treat as she's very fond of watching videos and observes them very intently," Ms Singh said.
Since Rita doesn't leave her enclosure much, a big screen will be put up outside from where children, journalists and visitors will be able to see her.
The chimpanzee has spent more than half her life in Delhi. From 1985 to 2006, she was loaned to a zoo in Punjab for a breeding programme.
Chimps only live up to about 40 years in the wild, but can last much longer in captivity, reports BBC.