Udi (also called Uti or Udin) is a language spoken by the Udi people and a member of the Lezgic branch of the Northeast Caucasian language family. It is believed an earlier form of it was the main language of Caucasian Albania, which stretched from south Dagestan to current day Azerbaijan. The Old Udi language is also called the Caucasian Albanian language and possibly corresponds to the "Gargarian" language identified by medieval Armenian historians. Modern Udi is known simply as Udi.

The Udi language can most appropriately be broken up into five historical stages:

Soon after the year 700, the Old Udi language had probably ceased to be used for any purpose other than as the liturgical language of the Church of Caucasian Albania.

The language is spoken by about 4,000 people in the village of Nij, Azerbaijan, in Qabala District, in Oghuz District, as well as in parts of the North Caucasus in Russia. It is also spoken by ethnic Udis living in the villages of Debetavan, Bagratashen, Ptghavan, and Haghtanak in Tavush Province of northeastern Armenia, and in the village of Zinobiani (former Oktomberi) in the Qvareli Municipality of the Kakheti province of Georgia.

Udi is endangered, classified as "severely endangered" by UNESCO's Red Book of Endangered Languages.

Old Udi, unlike modern Udi, did not have the close-mid front rounded vowel /ø/. Old Udi contained an additional series of palatalized consonants.

The Old Udi language used the Caucasian Albanian alphabet. As evidenced by Old Udi documents discovered at Saint Catherine's Monastery in Egypt dating from the 7th century, the Old Udi language used 50 of the 52 letters identified by Armenian scholars in later centuries as having been used in Udi language texts.

In the 1930s, there was an attempt by Soviet authorities to create an Udi alphabet based on the Latin alphabet, as shown in the image, but its usage ceased after a short time.