A subnotebook or ultraportable is a class of laptop computers that are smaller and lighter than typical notebooks.

This category of computers can range in price from high end high capability models at $2,000 to low end low capability models at $250.These computers are often confused with the "Ultra-Mobile PC" category, which is the name of a platform of small form-factor tablet PCs. Unlike UMPCs, they generally are found to run full desktop operating systems such as Windows or Linux, rather than specialized software such as Windows CE, Palm OS or Internet Tablet OS.

Subnotebooks are smaller than laptops but larger than handheld computers. They often have smaller-sized screens, less than 14 inches, and weigh less than typical laptops, usually being less than 2 kg (4.4 lbs). The savings in size and weight are usually achieved partly by omitting ports or having removable media or optical disc drives. Many can be paired with docking stations to compensate.