The festival is opened by the symbolic "Flight of the Dove", performed this year by Italian Olympic swimmer Federica Pellegrini.
The "dove" flies from the bell tower in St Mark's Square.
Thousands of people flock to Venice for 10 days of street theatre, pageants and masked balls.
The festival runs for 12 days, until Tuesday 20 February.
The carnival is thought to date back to the 12th Century. People wore masks so they could flirt and gamble without being recognised.
A mask provides the wearer with complete anonymity.
This year's festival marks the 300th anniversary of the birth of Venetian playwright, Carlo Goldoni.
The activities also include climbing on the bell tower in St Mark's Square.
People go to elaborate lengths to dress in 18th Century style, the heyday of the carnival.