A subnotebook is a small and lightweight portable computer, with most of the features of a standard notebook computer but smaller. The term is often applied to systems that run full versions of desktop operating systems such as Windows or Linux, rather than specialized software such as Windows CE, Palm OS or Maemo.

Subnotebooks are smaller than notebook computers but larger than handheld computers and ultraportables. They often have screens that are 26,5cm = 10.4″ (diagonal) or less, and weigh less than 1 kg; as opposed to full-size laptops with 30,5cm =12″ or 38cm = 15″ screens and weighing 2 kg or more. The savings in size and weight are usually achieved partly by omitting ports or having removable media/optical drives; subnotebooks are often paired with docking stations to compensate.

Subnotebooks have been something of a niche computing product and have rarely sold in large numbers until the 2007 introduction of the Asus Eee PC and the OLPC XO-1http://www.itworld.com/Tech/2987/070215olpc/.