Jeans are now a very popular form of casual dress around the world. They come in many styles and colors, however "blue jeans" are particularly identified with American culture, especially the American Old West. Americans spent more than $14 billion on jeans in 2004.

Trousers made from corduroy or canvas are sometimes called "jeans". However, by definition the word "jeans" strictly refers to trousers made out of denim.

The word "jeans" comes from the French phrase bleu de Gênes, literally the blue of Genoa. Jeans fabric, or denim, originated independently in two places: the French town of Nîmes, which 'denim' owes its name to; and in India, where trousers made of denim material were worn by the sailors of Dhunga, which came to be known as dungarees.

At around the same time, denim trousers were made in Chieri, a town near Turin (Italy), during the Renaissance, and were popularised in the 16th century. These trousers were sold through the harbour of Genoa, which was the capital of the independent Republic of Genoa which was a naval power.

Early examples of these trousers were made for the Genoese Navy, which required all-purpose pants for its sailors. They required pants that could be worn wet or dry, the legs of which could easily be rolled up to wear while swabbing the deck. These jeans were laundered by dragging them in large mesh nets behind the ship, and the exposure to sea water and sun would gradually bleach them to white. They were especially worn by Genoan sailors and stevedores who worked in Italy and France, and in 1860, during the Battle of Marsala, Sicily, were worn by general Giuseppe Garibaldi and his Italian troops.

Traditionally, jeans were dyed to a blue color using natural indigo dye. Today, it is more common to use synthetic indigo dye or sulfur dye.

A German-Jewish dry goods merchant Levi Strauss was selling blue jeans under the "Levi's" name to the mining communities of California in the 1850s. One of Strauss's customers was Jacob Davis, a tailor who frequently purchased bolts of cloth from the Levi Strauss & Co wholesale house. After one of Davis's customers kept purchasing cloth to reinforce torn pants, he had an idea to use copper rivets to reinforce the points of strain, such as on the pocket corners and at the top of the button fly. Davis did not have the required money to purchase a patent, so he wrote to Strauss suggesting that they both go into business together. After Strauss accepted Davis's offer, the two men received U.S. patent 139,121 , for an "Improvement in Fastening Pocket-Openings," on May 20, 1873.

In 1885 jeans could be purchased in the US for $1.50 (approximately $34 in 2007). Today, an equivalent pair of jeans can be purchased for around $80, but more stylish pairs can cost much more.