Miss Hungary, Edina Kulcsar, was the runner-up and Miss United States, Elizabeth Safrit, came third in the 64th annual competition, contested by women from 121 countries.
Strauss clasped her hands together in surprise and was presented with the sash by the outgoing Miss World, Megan Young of the Philippines.
The medical student sat in the winner’s throne as the 2013 champion put the glittering crown on her head before a fireworks finale at the ExCeL exhibition centre in east London.
“South Africa this is for you,” Strauss said afterwards.
“I think I will brace myself for what’s about to happen. It’s a huge responsibility.”