The Chrysler 300 "letter series" are high-performance personal luxury cars that were built by Chrysler in the U.S. from 1955 to 1965 and were a sub-model from the Chrysler New Yorker. After the initial year, which was named C-300 for its standard 300 hp (220 kW) 331 cu in (5.4 L) FirePower V8, the 1956 cars were designated 300B. Successive model years were given the next letter of the alphabet as a suffix (skipping "i"), reaching the 300L by 1965, after which the model sequence was discontinued while the "300" remained. At its introduction it was advertised as "America's Most Powerful Car".

The 300 "letter series" cars were among the vehicles built by Chrysler after World War II that focused on performance, and thus can be considered the beginning of the muscle car, though full-sized and more expensive. Chrysler had a long history of producing race car products going back to the Chrysler Six that was entered in the 1925 24 Hours of Le Mans, 1928 24 Hours of Le Mans, 1929 24 Hours of Le Mans, and the Chrysler Imperial Eight roadster in the 1931 24 Hours of Le Mans. The 1955 C-300 and the 1956 300B were raced with very little modification at NASCAR races to include Watkins Glen International where it won races multiple times.

The automaker reintroduced the 300 designations again for performance-luxury sedans in 1999, using the 300M nameplate from 1999 to 2004, and expanding the 300 series with a reintroduction of a new Hemi-engineered V8 installed in the 300C, the top model of a new Chrysler 300 line, a new rear-wheel drive car launched in 2004 for the 2005 model year.