According to the Bellingham Herald's David Rasbach, Ridnour announced his plans Tuesday.
"I'm retired," he said. "I’m not going to go back. I think I knew it last summer; I just didn’t say it."
A 12-year veteran selected in the first round of the 2003 NBA draft by the Seattle SuperSonics, Ridnour spent the first five years of his career in the Pacific Northwest.
Following a fairly underwhelming rookie season, Ridnour emerged as a starter for the Sonics and averaged better than 10 points and five assists during each of the next three campaigns.
The University of Oregon product was then shipped to the Milwaukee Bucks in August 2008, and he resided in Wisconsin for two years before signing with the Minnesota Timberwolves as a free agent. Ridnour then made his way back to the Bucks as part of a 2013 three-team trade with the Oklahoma City Thunder.
From that point on, Ridnour bounced around between Milwaukee, the then-Charlotte Bobcats and the Orlando Magic before he encountered a slew of trades last summer.
"Honestly, I think I'd pretty much made my decision before that," Ridnour said of last summer's trade wave, per Rasbach. "It was funny to watch all the people get pumped up and write about it and all the craziness of those couple days."
All told, Ridnour finished his career with averages of 9.3 points, 4.5 assists, 1.0 steal and a field-goal percentage of 43.1.
And while the 35-year-old has yet to officially inform the NBA of his decision to retire, he told Rasbach he will file paperwork "pretty soon."