Thousands of people are expected at central London's Trafalgar Square to celebrate Diwali - the Hindu festival of light.
People will get the chance to learn traditional dances and songs and the square will be lit up with lanterns during the free event.
To coincide with the occasion, the National Gallery will have artists and musicians performing Hindu tales.
The Greater London Authority-organised event started at 1500 BST.
The word Diwali is an abbreviation of Deepavali, which means "cluster of lamps", and the festival is a celebration of good over evil.
London Mayor Boris Johnson said: "Diwali is a wonderful festival that can be enjoyed by every community.
"Diwali is an occasion of great significance to Hindus, Sikhs and Jains, but with its underlying themes of peace, renewal and co-operation, it has relevance and meaning for all Londoners."