The British comic star is said to be setting his sights on the Far East for his big day and wants to Jet off to Japan to wed the pop beauty, despite their friend Rihanna saying they plan to tie the knot in India - where the couple got engaged.
A source said: "Russell and Katy are marrying at the end of the year, almost a year to the day he proposed.
"They originally planned to wed in India within the grounds of the Taj Rambagh Palace hotel, where Russell popped the question. The pair have a holding reservation but nothing is set in stone yet.
"They want to keep people guessing about the ceremony - even their celebrity pals.
"While he was in Los Angeles, Russell told a couple of people that they were also considering Tokyo as a venue. It's a buzzy, vibrant city and somewhere completely different and unique. Katy kept jokingly hitting Russell, telling him to keep his big mouth shut."
However, Katy is now so keen on a Japanese wedding she has been looking to purchase a Geisha-inspired gown.
The source added to the Daily Mirror newspaper: "She really likes the idea of wearing some kind of Geisha-inspired bridal dress, so Tokyo is a real possibility."
The 'I Kissed a Girl' hitmaker is reported to be keen on an unusual gown, and is looking for something to make her "stand-out".
An insider said: "She knows her toned torso is her best feature, so she wants to show it off.
"She's also more than aware that her wedding photos will be seen the world over, so she knows her look needs to stand out. From the back, she wants to look like a traditional bride, with a very long train, but from the front, she wants a Vegas-style sequined number with exposed skin."