Perhaps the hottest secret girlfriend of all time...possibly for both Bobby and John F. Kennedy!
Yes, this secret girlfriend isn't so secret anymore after David Letterman's very public revelation of their in-office affair.
Mistress to FDR himself, originally hired as personal secretary to Eleanor Roosevelt (can you really blame the guy?).
Secret girlfriend of actor Billy Crudup, Danes actually tore him away from Mary Louise Parker when she was 7 months pregnant with her son. Yikes.
Oh c'mon! Did you reeeeally think this list could exist without mentioning that familiar spermy-dressed gf who ruled the 90s!?
Mistress to King Henry VIII, she later had him annul his marriage then marry her. Not so secret afterall....
Not only was Heidi Fleiss a secret girlfriend to Hollywood royalty like Marlon Brando, she employed a number of ladies of the night that secretly served married men throughout Hollywood.
Hunter is one of the secret girlfriends we really wish had stayed secret -- after all, John Edwards' wife was going through chemo! Too cold.
Like most secret girlfriend scenarios, Fisher's relationship with Joey Buttafuoco did NOT end well, but did result in a somewhat popular sex tape.
Camilla's decades-long secret girlfriend status to Prince Charles solidified "poor eye sight" on the list of unfortunate genetic traits among British royals. Seriously Charles? You had this.