LORI L: I bought this dress for my daughter. She is about 5'1" and 108 lbs. I got an XS and it is pretty snug. At the time I bought it there were no other sizes to choose from so I took a gamble. At 5'11", and don't think it would be considered "long" for you in the front and possibly more like tea length. The back length would probably be okay because it has a train but I don't think it would "drag" behind you like a small train would. I hope this is helpful for you.
The dress is ABSOLUTELY beautiful and actually as pretty as it is in the picture, it doesn't do it justice.

Christine P: My daughter is 5'4", and this dress is still a little long with her 3" heels. The toes of the shoes just peek out under the dress. I'd suggest ordering it, try it, and return if it doesn't work.

Angie H: It would be perfect then!! We used this dress as a bridesmaid dress in my wedding and it fit them all, but most had to take some off the bottom because it was too long. My cousin is 5'8" and took four inches off of it, hemmed it and it still covered her feet. I cannot even understand why it is that long.

Angie H: It is very long! Otherwise it fits great for curvy or petite frames. The back is see through so you need to find a good bra or whatever it is that you plan to wear underneath.