343 may refer to:
343, a year of the Christian or Common Era 343 BC, the year 343 (number), the integer represented by the English-language numeral "three hundred and forty-three"
Vehicles Three Forty Three, a New York City fireboat Volvo 343, a small family car Fiat 343, a bus
Other uses 343 Guilty Spark, a fictional character from the Halo franchise Halo Studios (formerly known as 343 Industries), a Microsoft video game studio responsible for the Halo franchise, named after this character Area code 343, a phone number area code for Ottawa, Ontario, Canada Highway 343, a list of highways numbered 343 343, a group of women behind the Manifesto of the 343 Asteroid 343, see 343 Ostara