The Fasnacht festivities began at 4am with a parade of masked participants in costumes carrying lanterns through the streets of the city centre, where all lights were turned off.
Pipers, drummers and other musicians took part in the cortege.
An estimated 18,000 people marched in the parade, known in German as the Morgestraich, with thousands of spectators lining the streets to take in the colourful spectacle.
The event, which traditionally starts on the Monday after Ash Wednesday, marks the beginning of 72 hours of partying in the country’s third largest city.
The carnival follows others held around Switzerland. Whereas those are Catholic events to mark the festive period that occurs before Lent, a period of fasting in the Christian calendar, Basel’s Fastnacht is unique for being Protestant.
Each year the parade that begins the carnival features various themes, typically drawn from topical current affairs.
This year, the Greek government debt crisis and associated Eurozone problems, along with the strong Swiss franc, were among the popular themes used by parade participants.
The parade also included Switzerland’s decision to abandon nuclear power and the problems linked to the Fukushima disaster in Japan.
The Fasnacht began in cool, crisp conditions, drawing onlookers from across Switzerland and Europe.
Lanterns from the parade will remain on display in the square in front of Basel’s cathedral until Wednesday.
Concerts and a children’s day on Tuesday are among the related events during the three-day carnival, with many restaurants and bars in Basel’s Old Town remaining open for 72 hours straight.