The 49-year-old actress told her five million followers that she'd changed her Twitter name to @justdemi.
Demi and Ashton Kutcher – who became celebrated users of the site, often posting candid pictures of themselves and talking about their relationship – announced the end of their marriage in November.
In April, Demi asked her followers on the site for suggestions for a new handle.
TV personality Piers Morgan suggested: "How about @mrsmorgan?" but was politely rebuffed.
Demi said she would "have to get clever" because so many names on the popular site have already been claimed.
She wrote that it was "so hard finding a name that was fun, somewhat playful and available", adding that the new moniker "could grow" on her.
Special report: Why the Hollywood heroine will survive divorce
In pictures: When life was tweet for Demi and Ashton