She cited irreconcilable differences in a court document submitted Tuesday in Santa Monica, California.
Heidi and Pratt are stars of the MTV series "The Hills" and have been married since last April. The series is in its final season.
Her two-page handwritten filing does not offer any more details on the couple's breakup. An e-mail sent to an MTV spokeswoman seeking comment was not immediately returned.
The filing also doesn't indicate whether heidi intends to file for divorce, which would formally end their marriage.
Watch her video: