Human resources graduate Ivian Lunasol Sarcos Colmenares, 21, of Venezuela, beat 113 contestants to the crown at Earl’s Court in London.
Both Miss Mounter and fellow British contestant Miss Scotland, Jennifer Reoch, made it through to the final seven.
The 23-year-old is originally from Beddau, near Pontypridd, but qualified for the Miss England competition because she was living in London while studying journalism at Roehampton University.
Miss Mounter said: “I’m really happy and tired. It was a breathtaking experience.
“I’m happy whatever the outcome, I’m that kind of person. I think things are meant to happen for a reason.
“I’m really over the moon.”
Sir Bruce Forsyth was in the front row for the 60th Miss World final, which saw performances from dance group Diversity and boyband Blue.