"A.D.T.O.Y." () is a song recorded by South Korean boy group 2PM for their third Korean studio album Grown. It was released by JYP Entertainment on May 11, 2013.
On April 30, 2013, JYP Entertainment revealed the title and track list of 2PM's third studio album, which would feature a double title track: "Comeback When You Hear This Song" and "A.D.T.O.Y.", which stands for "All Day Think (of) Only You". On May 6, 2013, 2PM released eleven of the twelve songs from their upcoming studio album Grown as a digital pre-release. On May 11, "A.D.T.O.Y." was released as a digital single along with its music video, following the group's first performance of the song on a comeback special aired on MBC titled 2PM Returns.
"A.D.T.O.Y" was written and composed by JYP Entertainment founder Park Jin-young, with the rap section co-written by 2PM member Taecyeon. The song is composed in the key B major at a rate of 148 beats per minute and a running time of 4 minutes and 6 seconds. "A.D.T.O.Y." is an electropop and R&B track that mixes repetitive violin, drums, and bass instrumentation with electronic dubstep sounds and layered breathy vocals. The lyrics of the song are about the intense intimate feelings of a man in love.
The music video for "A.D.T.O.Y.", starring actress , was released on May 11, 2013. The music video is filmed in black-and-white and features a choreography using chairs and incorporating sensual hip and pelvic movements. It received attention for what was described as "R-rated" scenes involving the members shirtless and being intimate with the actress in various set locations such as in bed, in a car, and in a bathroom. JYP Entertainment stated that more explicit scenes were removed during the editing process of the music video in order for it to receive a 15+ rating instead of a 19+ rating by the Korea Media Rating Board.
2PM first performed "A.D.T.O.Y." on their comeback special aired on MBC titled 2PM Returns. On May 16, 2013, 2PM held their first comeback stage for the song on Mnet's M Countdown; they went on to promote the song on Korean music programs for five weeks. They also performed the song on TV shows such as You Hee-yeol's Sketchbook and the third season of the South Korean edition of Dancing with the Stars.
Following the resurgence in popularity of 2PM's 2015 title track "My House" in 2020, "A.D.T.O.Y." also saw a smaller increase in attention. As a result, when promoting their comeback album Must in 2021 after a four-year hiatus due to mandatory military service, 2PM also performed "A.D.T.O.Y." on their Mnet comeback show special Must on June 28 and on MBC's Show! Music Core on July 3.
Billboard praised the "emotional intensity" of the song, which had a unique "sexy concept" at a time when the concept was generally deemed as a girl group concept in South Korea. Another Billboard article described "A.D.T.O.Y." as a song that "Usher would kill for". The song topped various domestic music charts such as Bugs! and Soribada upon release, but performed better with international audiences than it did with domestic audiences.