Powerful Movies about loneliness

FernTree -
The Omega Man gets my vote of your list. Phenomenal movie in virtually all regards (the now dated aesthetic notwithstanding), and really one of Heston's best performances. As much as I appreciated the recent I Am Legend, The Omega Man trumps it on so many levels if compared.

I don't know that it's one of the more quintessential "lonely" films that comes to mind if we're talking strictly classic introvert/reclusive with all of the correspondent psychological baggage one associates with loneliness.

Sybil, The Fisher King, Tideland, Being John Malkovich, Mary Shelley's Frankenstein, Eraserhead, The Assassination of Richard Nixon, Lars and the Real Girl, Reign Over Me, The Machinist, A Pure Formality (Una Pura formalità), A Tale of Two Sisters (Janghwa Hongryeon ), Jermiah Johnson, Vanishing Point, Smart People, One Hour Photo, A Beautiful Mind, Conspiracy Theory, The Conversation, Rebel Without A Cause, and several of the previously mentioned come to mind.

There's so many more that I'd need to think about to remember, I suppose it comes down to semantics at some point. Most of Lynch's movies for example share a quality of complete isolation or loneliness/despair throughout his films. Kubrick is often the same. I don't think I've ever quite seen such a compelling and believable portrayal of isolation and its subsequent effect than I had in the Shining, or 2001 a Space Odyssey. If your definition/criteria is simply loners, that narrows it quite a bit.

.

I Am Legend.

Here's a film that I forgot to add in that's a clear-as-the-light-of-day depiction of loneliness:

The Loneliness of the Long-Distance Runner.

__________________
Health is the greatest gift, contentment the greatest wealth, faithfulness the best relationship.
Buddha

An oldie but what The Old Man and the Sea, also Alien and Enemy Mine.

As it was on again the other day, I must say I like The Pornographer.

It's weird that you've bumped two different threads with that guy Earl Gray as the last poster.

I don't think this movie was about loneliness either...this guy was spoiled and self-absorbed and entitled and wanted to rebel against all of that. He spends a lot of his journey in the film alone, but I don't think he was lonely and I don't think that's what the movie was about.

Taxi Driver is the first film I thought of on this subject...I think this character was all about loneliness, even if he didn't realize it.

I thought that 7 Chinese Brothers with Jason Schwartzman was a funny and ultimately sad look at Loneliness, really enjoyed the movie.

Swiss Army Man
Lars von Trier's Depression Trilogy?

The Heart is a lonely Hunter

Gravity

Her (2013) fits that too!

Georgy Girl is also a powerful movie about loneliness, as is Midnight Cowboy.

__________________
"It does not take a majority to prevail, but rather an irate, tireless minority, keen on setting brush fires of freedom in the minds of men." -- Samuel Adams (1722-1803)

Lars and the Real Girl was a surprisingly charming movie.

Pink Floyd's The Wall is definitely a movie about loneliness, in a rather intense way.

agreed, Her was a great film about a man being alone despite being surrounded by people.

EXOTICA

I'd say Permanent Record starring Keanue Reeves. I saw the film late one night when I was a teenager and I remember it made me cry and, for me, highlighted how hard teenage life was and how alone I felt even when with my friends. I actually called my best friend Al and he admitted he was at home crying too lol A weird time in most lads life I'd say.