Louis Marx and Company was an American toy manufacturer from 1919 to 1978. The Marx logo was the letters "MAR" in a circle with a large X through it, resembling a railroad crossing sign. Because of this, Marx toys are sometimes misidentified as "Mar" toys.

Marx's toys included tinplate buildings, tin toys, toy soldiers, playsets, toy dinosaurs, mechanical toys, toy guns, action figures, dolls, dollhouses, toy cars, and HO scale and O scale toy trains. Marx's less-expensive toys were extremely common in dime stores, and its larger, costlier toys were staples for catalog retailers such as Sears and Montgomery Ward, especially around Christmas. Although the company name is now largely forgotten except by toy collectors, several of the brands it developed remain strong icons in popular culture: Rock'em Sock'em Robots, introduced in 1964, was a Marx staple for years, and its best-selling sporty Big Wheel tricycle, which was introduced in 1969, and became one of the most popular toys of the 1970s, is enshrined in the National Toy Hall of Fame.

In 1972, Marx sold his company to the Quaker Oats Company for $54 million ($246 Mil. in 2005 dollars) and retired at the age of 76. Quaker owned the Fisher-Price brand, but struggled with Marx. Quaker had hoped Marx and Fisher-Price would have synergy, but the companies' sales patterns were too different. Marx has also been faulted for largely ignoring the trend towards electronic toys in the early 1970s. In late 1975, Quaker closed the plants in Erie and Girard, and in early 1976, Quaker sold its struggling Marx division to the British conglomerate Dunbee-Combex-Marx, who had bought the former Marx UK subsidiary in 1967.