*As if Tyra Banks doesn’t have enough to worry about, the former model has asked a judge for protection from a “mentally unstable celebrity stalker.”

In the documents, filed in L.A. County Superior Court and obtained by TMZ, Tyra seeks a restraining order against 39-year-old Marten Williams, Jr. — 6’2″, 220 lbs — claiming he has “targeted and harassed and stalked” Tyra and her family since 2006.

She claims the man has a history of mental illness — and that he believes “he killed George Bush Jr. and that Michael Jackson is alive and living in Long Beach.”

Tyra also claims the man has left several “ominous frightening letters and items” at her Beverly Hills home — including his prescription medication, L.A. County jail wristbands and an invitation to a wedding ceremony set for 1/08/11… the day he believes he will marry Tyra.

In the docs — filed by top gun lawyer Evan Spiegel — Tyra states, “I am in fear from Mr. Williams for my personal safety, and that of those around me, including my family and employees.”

Williams was just arrested earlier this month for trespassing on Tyra’s property. Williams told police he was bringing Tyra “offerings.” He was later placed on a 5150 psychiatric hold, but Tyra’s people believe he may have already been released.

Tyra wants Williams to stay at least 100 yards away from her and her family — fearing that his conduct will “likely continue and escalate” unless the court steps in.

As previously reported, the mother of a teenage girl who appeared as a self-described sex addict on “The Tyra Banks Show” has sued host, Warner Bros. Entertainment and the executive producers of the show, alleging they flew the girl to New York and put her on TV without parental consent or the proper work papers from the state of Georgia.