KQSR (100.9 FM) is a commercial radio station in Yuma, Arizona, also serving El Centro, California. The station carries a classic hits format as "100.9 The River."

The station operates at 3,000 watts Effective radiated power (ERP), making it a Class A station. However, KQSR has been granted a U.S. Federal Communications Commission construction permit to upgrade to Class C2, increase ERP to 50,000 watts and decrease HAAT to 78 meters.

The station used to be known as "The Jet" and aired a classic rock format. It adopted the slogan "Star 100.9" and aired an adult contemporary format. In May 2009, Jeff Edwards, who hosted the weekday midday show from 10 am–3 pm, became Program Director. His show included The '80s Lunchbreak, an all-1980s hour from 11 am to 1 pm. Jeff Edwards also hosted a Saturday morning 1970s show, 70's Spotlight Saturday from 8 am until noon. Currently, the station is known as "100.9 The River" under the format of Classic Hits. The Bob and Tom syndicated morning show is the anchor for the station with local talent Jonny Porter from 10 am to 3 pm and Dave Nash from 3 pm to 7 pm.

On December 15, 2023, KQSR flipped to Classic hits. The station rebranded as "100.9 The River," and adopted the slogan "Yuma's Classic Hits." KQSR is the only Rock music/Classic Rock/Classic Hits station in the Yuma area.

• Official Website
• Facility details for Facility ID 12660 (KQSR) in the FCC Licensing and Management System
• KQSR in Nielsen Audio's FM station database

32°38′31″N 114°33′36″W / 32.642°N 114.560°W / 32.642; -114.560