Miss Hungary, Edina Kulcsar, was judged the runner-up and Miss United States, Elizabeth Safrit, came third in the 64th annual competition, contested by women from 121 countries.
Medical student Strauss clasped her hands together in surprise and was crowned by the outgoing Miss World, Megan Young of the Philippines, to huge cheers in the ExCeL exhibition
"South Africa this is for you," Strauss said. "I think I will brace myself for what's about to happen. It's a huge responsibility."
She told AFP she wanted to help spread education in her homeland and thereby help other people
"I am what I am today because of the opportunities I have received and I would love to give others the same opportunities; educating, the opportunity to be educated, to make healthy choices and also to live their dreams," Strauss said.
And she was already getting used to the glittering crown.
"I'll definitely keep it on as long as I can but my parents are staying around here so they'll be hugging me and I'm afraid that it might fall off," she said.
This year's event has been rocked by the murder of Miss Honduras, 19-year-old Maria Jose Alvarado, who was shot dead along with her sister last month.
Police in Honduras accuse her sister's boyfriend of shooting them after seeing his partner dancing with another man at a party.
Shimmering costumes
Strauss and
"We hope that it will really start to impress on the people in Honduras that the violence, and hurting people like those two innocent women...
Sunday's show started with a spectacular choreographed dance routine, with all the beauty queens on stage in costumes inspired by their homelands -- including Miss Bolivia in a
While beauty remains central to the event, the women taking part are chiefly judged on their talents and involvement in good causes.
Miss Malaysia won the talent competition in a live sing-off with Miss Scotland.
In the Beauty with a Purpose section -- the heart of Miss World -- contestants present a charitable project they have been working on in their homeland.
In this section, the judges gave equal first place to Misses Brazil, Guyana, India, Indonesia and Kenya, unable to separate them.
In rounds held since the contestants arrived in London, Miss Finland topped the sporting competition; Miss United States was the multimedia winner; Miss Bosnia and Hercegovina won the top
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