"Check on It" is a song by American R&B singer Beyoncé Knowles, featuring American rapper Slim Thug. It was written by Knowles, Kasseem "Swizz Beatz" Dean, Sean Garrett, Angela Beyincé and Stayve Thomas, and produced by Knowles and Swizz Beatz for the 2006 film The Pink Panther, in which Knowles co-stars. Although not included on its soundtrack album, the song is included on Destiny's Child's greatest hits album #1'sand on selected non-U.S. versions of Knowles' second solo studio album, B'Day.

Knowles said that the song started out as a joke, and that the title "Check on It" was jokingly used with her and her management before they decided to turn it into a song. However, the song's lyrics bluntly talks about a woman's booty.

"Check on It" was released on Knowles' former group Destiny's Child's greatest hits, #1's'. It was not originally intended for release as a single from the album #1's. However, it received heavy rotation in US radio stations than the first single, "Stand Up for Love". Because of this, "Check on It" debuted on the Hot 100 in late 2005. A remix of the song was made, which features fellow Houston artist Bun B.

"Check on It" reached number one on the Hot 100 in its twelfth week on the chart, becoming Knowles' third number-one as a solo artist and Slim Thug's first. The single remained at number-one for five consecutive weeks, tying Canadian singer Daniel Powter's 2005 single "Bad Day" for the longest-running number-one single in 2006. It was certified platinum by the RIAA for net shipment of 800,000 paid downloads. "Check on It" achieved crossover success, peaking at number one on the Rhythmic Top 40 and Hot Dance Club Play charts, and at number three on the Hot R&B/Hip-Hop Songs chart. It also reached number one on the Pop 100, becoming Knowles' first entry on the chart. It was the eighth most played song of 2006 on the radio, being played 290,231 times.

It became Knowles' fifth top-twenty hit in Canada in late 2005, and in February 2006 the song climbed to number twenty on the Canadian BDS airplay chart for a second time. The song reached the top five in Norway and the Netherlands, the top ten in Europe, Switzerland, Austria and Brazil, and the top twenty in Germany and Sweden. In the UK the song debuted at number four before rising to number three the week later, selling 122,500 copies.

When demand was growing for the song, Knowles shot a music video serving as promotion for both #1'sand The Pink Panther. The video was directed by Hype Williams, and was premiered on December 16, 2005. The remix of the song in the music video features a remix of "The Pink Panther Theme" and a rap from Bun B. "Check on It" won on August 31, 2006 the 2006 MTV Video Music Award for Best R&B Video.

The video has a pink theme to fit in with The Pink Panther. Knowles is shown in mostly all pink, and the dancers wear PVC jackets and dance around rippling satin sheets. The video also features Knowles bending over and grabbing her behind. The video cuts to Knowles wearing a polka dot corset against a hot magenta polka dot wall, wearing a pink wig and pink lipstick. Where black bars normally appear on a 4:3 (full screen) television showing a widescreen production, footage is displayed of curtains moving in the background. This was a trend in Hype Williams' videos during that year.

The video was featured on the DVD of the film.