12.3 million passengers used the airport last year – a rise of 16.9%.
Passenger numbers for December were up 18.9%.
Four new airlines started flying from Luton in 2015 and 20 new routes were launched.
The airport is currently undergoing a £110 million redevelopment, which when complete will boost capacity by 50% to 18 million.
Nick Barton, chief executive of LLA, said: “With more than 12 million passengers passing through the airport 2015 was a record year for LLA.
"But while 2015 was the busiest year in our history, 2016 is set to be the most exciting as our £110m investment transforms the experience for our passengers."
