Aside from being among the only 300 or so people who have done so, Rachel is the first Australian woman to take the title, and Marty is the first Slovakian woman.
The pair, who founded the blog Very Hungry Nomads to document their travels, met more than 16 years ago – fittingly, while on a 49-day overland tour of Europe. Marty was the tour guide and Rachel was the on-road chef.
Since then, they've scaled Mount Everest, trekked with mountain gorillas in Uganda, sat among the ancient ruined Pyramids of Sudan and learned a lot about themselves in the process.
Including which countries they'd go back to, time and time again.
For Rachel, there's only one answer: Thailand.
Watch Marty and Rachel talk about their trek around the world on The Project. Post continues after video.
"It was one of the first countries I ever went to when I was in my 20s because it is so easy to get to from Australia," Rachel tells Mamamia.