A laptop computer, or simply, a laptop is a small mobile personal computer that has components that are similar to their desktop counterparts but are optimized for mobile use and efficient power consumption. Laptops usually have a built-in keyboard and typically employ liquid crystal displays (LCD). There are several categories of laptops like Ultra-Mobile Personal Computers (UMPC), Ultra-portables, Thin-and-Lights and Mainstream.

Laptops are also known as notebook computers or simply notebooks. A laptop generally runs on a single main battery and is capable of doing the same tasks as a desktop computer can. For a given price range, laptops are generally less powerful than a desktop computer as they prioritize their compactness and energy efficiency over absolute performance. Thanks to advances in dual-core processors and perpendicular recording, laptops are giving tough competition to PCs.

Bill Moggridge's designed GRiD Compass 1101 is widely regarded as the first true laptop which was released in 1982. Laptops have an in-built touch-pad or track-pad for input, though an external mouse can also be attached. Ultra-portables are mostly used by business travellers as they are very light (1.4 kg to 2.3 kg), have an extended battery life and are often very expensive. They generally do not have full size keyboards and their screens usually measure less than 30 cm diagonally. UMPCs are extremely portable as their size matches with that of the Personal Digital Assistants (PDAs).

Most modern laptops feature a 30.5 cm or larger active matrix displays with resolutions of 1024 x 768 pixels and above. High-end laptops like the Dell Inspiron E1505 and E1705 come with advanced features. Current models of laptops use lithium-ion or lithium polymer batteries that can last for hours with light-duty use. Intel, AMD and VIA have developed a wide range of laptop specific processors; Hewlett-Packard, Compaq, Acer, Apple and Dell are among the leading manufacturers of laptops.