A lap dog gets its name from its size; it is small enough to be held in the arms or lie comfortably on a human’s lap. Most lap dogs fall into the toy dog category.

Lap dogs have been used as pets, fashion accessories and status symbols. Popular culture presents the image of the spoiled or pampered ‘pooch’ who is the obnoxious companion of a spoiled or pampered lady, but it is widely believed that the lap dog originally served a purpose; to provide warmth for wealthy or fashionable European women. There are also lap dogs, among the terrier group, for example, which were first developed for active work.

A few lap dogs were apparently bred solely as pets; the Japanese Terrier is among these.

Lap dog is also used jokingly to refer to a dog of any size who likes to climb onto people's laps for affection.