The Boeing 737 Next Generation, commonly abbreviated as Boeing 737NG, is the name given to the -600/-700/-800/-900 series of the Boeing 737. This series followed the 737 Classic (-300/-400/-500) series, which began production in the 1980s. They are short- to medium-range, narrow-body jet airliners. Produced since 1996 by Boeing Commercial Airplanes, the 737NG is sold in four sizes seating typically 110 to 210 passengers.

A total of 4,015 737NG aircraft have been delivered by April 2012, with more than 6,200 on order. Its primary competition is with the Airbus A320 family. Upgraded and re-engined models in development as the 737 MAX series will eventually supplant the 737NG.

Prompted by the development of the Airbus A320, which incorporated ground-breaking technologies such as fly-by-wire and side-stick controls, in 1991 Boeing initiated development of an updated series of aircraft. After working with potential customers, the 737 Next Generation (NG) program was announced on November 17, 1993. The 737NG encompasses the -600, -700, -800 and -900 variants, and is to date the most significant upgrade of the airframe. The performance of the 737NG is essentially that of a new airplane, but important commonality is retained from previous 737 generations. The wing was modified, increasing its area by 25% and span by 16 ft (4.88 m), which increased the total fuel capacity by 30%. New quieter and more fuel-efficient CFM56-7B engines were used. These improvements combine to increase the 737's range by 900 nmi, permitting transcontinental service. A flight test program was operated by 10 aircraft; 3 -600s, 4 -700s, and 3 -800s.