Lao or Laotian is a language and is the official language of Laos. It is also spoken in the northeast part of Thailand. Lao, like the other languages of Laos, is written in an abugida writing system. The languages has variations, but the Vientiane dialect is considered the standard written form of Lao.

Lao and Thai are both Tai languages and are very similar to each other. In fact, speakers of northern Thai dialects and Lao claim that they can largely understand each other, making the dialects mutually intelligible.