Quechan or Kwtsaan (/kʷt͡sa:n/, Kwatsáan Iiyáa), also known as Yuma, is the native language of the Quechan people of southeastern California and southwestern Arizona in the Lower Colorado River Valley and Sonoran Desert. Despite its name, it is not related to the Quechua language of the Andes.

Quechan belongs to the River branch of the Yuman language family, together with Mohave and Maricopa languages. Publications have documented Quechan grammar and texts.

In 1980, it was estimated that there were fewer than 700 speakers of the language, including both the elderly and young. Hinton put a conservative estimate of the number of speakers at 150, and a liberal estimate at 400–500. As of 2009, 93 preschoolers were learning Quechan in the Quechan tribe's language preservation program, and the number of fluent speakers was estimated to be about 100. A Quechan dictionary was in progress.

In 2020, it was estimated that there were approximately 60 speakers of the language left.

Quechan speakers participate in the Yuman Family Language Summit, held annually since 2001.

A 2010 documentary, Songs of the Colorado, by filmmaker Daniel Golding features traditional songs in the Quechan language. Golding says, "The songs are all sung in the language, so if you're not learning and picking up the language, then you won't be able to understand the songs ... there are actually words telling stories..."

Assistance is available for speakers of the language who wish to vote in elections in Imperial County, California, and Yuma County, Arizona, under Section 203 of the Voting Rights Act of 1965.

Quechan has five vowel phonemes, which all occur in short and long forms. Vowel length is contrastive, as shown in ʔa·vé "snake" versus ʔa·vé· "mouse".