"Sadly, Katy and I are ending our marriage. I'll always adore her and I know we'll remain friends," Russell said in a statement to the Associated Press on Friday.
According to the TMZ, Russell, who filed in Los Angeles, cited "irreconcilable differences" as the reason for the split.
Russell was photographed over the holidays in London, without his wedding band on, while Katy was spotted in Hawaii, also without a wedding ring on her finger.
Russell and Katy married in October 2010.
Earlier this month, Russell spoke about the couple's plans to start a family, telling Ellen DeGeneres he longed to hear the pitter-patter of little feet.
"Katy says you are going to try and start a family. Are you going to have a family?" Ellen asked during an interview for "The Ellen DeGeneres Show."
"I would like one. I love those little babies in the beginning," Russell answered.
"Yeah, that's how they start out," Ellen chimed in.
"They're so lovely in that bit. Me and Katy are godparents to two twin boys. They're called Sam and Donovan," Russell said of the 1-year-olds.
"I can learn from them," Russell continued. "Me and Katy are their godparents, which means we're responsible for their spiritual growth. Should be interesting."
During his December "Ellen" visit, Russell also hit back at the rumors he and Katy had split.
"There are always rumors, aren't there? In the end you have to just not engage with Internet technology, which is difficult because [of] a lot of the nude women websites I quite enjoy," he said with a laugh. "But they've had to go. I've treated the whole Internet now like it's a wicked little liar.
"Yeah. I am really happily married," he said at the time.
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