The Q-Max or the Qatar Max is the largest liquefied natural gas (LNG) carrier class in the world. The name Q-Max refers to the maximum size of tankers capable of docking at the Ras Laffan terminal in Qatar. A typical Q-Max gas tanker is 345 m (1,132 ft) long, 53.8 m (177 ft) wide, and 34.7 m (114 ft) in height, with a draught of 12 m (39 ft). Ships of this type are the largest LNG carriers in the world. It has an LNG capacity of 266,000 cubic metres (9,400,000 cu ft), equal to 161,994,000 cubic metres (5.7208×109 cu ft) of natural gas. According to estimates, this amount of fuel can light up 70,000 U.S. homes for one year. Prior to Q-Max, Q-Flex ships were the largest LNG carriers with a maximum capacity of 217,000 m3 (7,633,283 cu ft).

Q-Max vessels are equipped with an on-board re-liquefaction system to handle the boil-off gas, liquefy it and return the LNG to the cargo tanks. The on-board re-liquefaction system allows a reduction of LNG losses, which produces economic and environmental benefits.