"Apt." is a song by New Zealand and South Korean singer Rosé and American singer-songwriter Bruno Mars. It was released through The Black Label and Atlantic Records on 18 October 2024, as the lead single from Rosé's upcoming debut studio album, Rosie (2024). It marked her first solo single in three years and her first release since departing from YG Entertainment and Interscope Records as a solo artist in 2023.

"Apt." was written and composed by various contributors, including Rosé and Bruno Mars. It is a pop, pop-punk, and pop rock track, featuring indie rock and electropop influences. It is inspired by a South Korean drinking game apateu (Korean: 아파트; lit. apartment), and the song's chorus is built around the game's rhythmic chant. Critics lauded the single for its catchy production and broad cross-cultural appeal.

"Apt." was a massive commercial success worldwide and debuted atop the Billboard Global 200 and Global Excl. US charts, earning Rosé and Bruno Mars their second number-one single on both charts. In South Korea, it became both artists' first track to attain a "perfect all-kill" and peak at number one on the Circle Digital Chart. The song also topped the charts in New Zealand, Australia, Hong Kong, India, Indonesia, Malaysia, the MENA region, the Philippines, Singapore, South Korea, and Taiwan. It entered the top ten on the US Billboard Hot 100 and the UK Singles Chart, becoming the first song by a K-pop female soloist to do so on either.