Robert Kraft has formally entered a not guilty plea in his prostitution case, according to court records obtained by TMZ Sports.
"The defendant Robert Kraft hereby pleads not guilty to all charges and requests a non-jury trial in the above-styled cause," the court docs state.
As we previously reported, Kraft's attorney accepted the summons from the court on Feb. 26 -- and an arraignment was set for March 27 at 8:30 AM ... the same day Kraft was expected to be at the NFL's Annual League Meeting with other team owners in Phoenix, Arizona.