The first actor / actress that you ever saw.......

[Trevor]

...... bare butt nekkid? 

For me, it was Candy Clark in The Big Sleep: I was eleven and had sneaked in to see this film. Quite a revelation to my eleven year old eyes. Sarah Miles, Joan Collins, Diana Quick and Candy in one movie? Wow: O V E R L O A D   O V E R L O A D  O V E R L O A D ........................

[retrorussell]

Probably Brooke Adams in INVASION OF THE BODY SNATCHERS (1978).  She may not have been seen from every angle but I was pretty shocked when her old body wrinkles in Donald Sutherland's hands and her naked body rises up behind him.  His eyes bug out in horror (and mine bugged out similarly, though in pleasant surprise). 

[Jack]

My folks took me to see Freebie and the Bean in 1974 and there was some topless girl in one scene.  My ten-year-old eyes 

[bob]

When I was a youngster my mom took me and my brother to see Forrest Gump. The scene where Robin Wright as Jenny is buck naked playing the guitar was beyond awesome for me at the time.

[Rev. Powell]

Lia Beldam (yum!) followed immediately by Billie Gibson (yuk!)

[alandhopewell]

     Dunno the actress' name, but she played a student in THE PRIME OF MISS JEAN BRODIE; she posed nude for one of the teachers, who was also her lover. I was 13.

[ChaosTheory]

Jeff Bridges & Rachel Ward in AGAINST ALL ODDS.  I was about 9.  Bridges was really something back in the day 

[JaseSF]

The first actress who played a character who was supposed to be nude in a film I watched was Tahnee Welch in Cocoon. The earlier cases where I recall nudity involved Jennifer Dale in Separate Vacations and Elizabeth Pena in Down and Out in Beverly Hills. I know I was in my teens by then. The first case where I saw full frontal nudity in a film I'm thinking was Mathilda May in Lifeforce...

[JoeTheDestroyer]

Tough to say.  Probably Adrienne Barbeau in Swamp Thing.  Not her best topless moment.

[FatFreddysCat]

I'm not even sure who it was anymore, but if memory serves one of the female cast members in "Private Benjamin" got topless for a brief instant. I don't think it was Goldie Hawn, it was probably one of the supporting cast members.

The reason it sticks in my mind is because "P.B." was the first "R" rated movie I ever saw (I was about 10 years old at the time) and my Mom, who was still pretty obsessive-compulsive about protecting my brain from bad influences in movies, attempted to cover my eyes when the topless scene happened, causing my father to holler "Dammit, leave the kid alone! He's been stealing my Playboy magazines for years now, he knows what they look like!" 

[alandhopewell]

     Not the first, or the last, but certainly noteworthy....
BURGESS MEREDITH!

[claws]

A topless Nastassja Kinski in For Your Love Only (1977) on German TV during prime time because Germans are anything but prude.

[HappyGilmore]

Hard to recall...but I would narrow it down to:

Topless- Linda Hamilton, Terminator 1. I saw 1&2 on VHS in the early '90s, and I was a young kid around 9/10.

Fully nude- Jenna Jameson in Private Parts, Howard Stern's big budget film debut.

[RCMerchant]

I think it was Angie Dickenson in BIG BAD MAMMA.

She was f**kin Captain Kirk!

[The Burgomaster]

Hmmm . . . tough to say.  But it was probably the scene in THE GODFATHER when Apollonia reveals her breasts.  I think that was the first R-rated movie I ever saw (in 1972 at the legendary Revere Drive-In, Revere, Massachusetts).