Ricky Burns is now full WBO lightweight champion after Mexican boxer Juan Manuel Marquez moved up to the welterweight division.
The Coatbridge fighter won the interim title with victory over Michael Katsidis in London in November.
However, Marquez retained the full title while he decided on his future.
"When I beat Katsidis I felt like a world champion, but this makes it all real and I'm thrilled I'm now the full world champion," said Burns.
"For the last 10 years I've been grafting away in my career, but in the last couple of years it has really taken off with me beating [Roman] Martinez and then beating a great warrior like Katsidis to put me up with the best in the world."
Burns, will defend his new title against former world champion Paulus Moses of Namibia in Glasgow on 10 March.
Britain now has two world champions, with Burns joining WBO light-heavyweight champion Nathan Cleverly among the elite.
"Nathan's a great fighter and Britain has now got two world champions to be proud of who can fly the flag on the world stage," added Burns, who stepped up a division to fight Katsidis after an impressive stint as WBO champion at super-featherweight.