Ampers&One (Korean: 앰퍼샌드원; RR: Aempeosaendeuwon; stylized in all caps) is a South Korean boy band formed and managed by FNC Entertainment. The group consists of seven members: Kamden, Brian, Jiho, Siyun, Kyrell, Mackiah, and Seungmo. They debuted on November 15, 2023, with the single album Ampersand One.

Ampers&One is a fusion of the symbol "& (ampersand)" and the word "one". The name reflects the group's wish "to achieve its dreams by coming together as a group".

Prior to the group's debut, Siyun was a trainee under YG Entertainment. He participated in YG's survival show YG Treasure Box in 2018 but was eliminated in the eighth episode.

In 2021, Kamden and Jiho participated in the MBC survival show Extreme Debut: Wild Idol but both were eliminated in the third episode.

In 2023, Kamden, Brian, and Jiho took part in the Mnet reality competition show Boys Planet, with Kamden and Jiho representing FNC Entertainment and Brian being a Yuehua Entertainment trainee. Jiho was eliminated in the fifth episode after ranking 55th. Subsequently, Brian ranked at 37th place and was eliminated in the eighth episode. Kamden participated in the finale, ranking 17th.

On September 5, 2023, FNC Entertainment announced that they would be debuting a seven-member boy group in early 2024. Later that month, on September 26, the agency announced a change of plans, with the group's debut brought earlier to November 2023. In the same press release, they confirmed Kamden and Jiho as the first two members of the lineup.

On October 18, FNC Entertainment announced that the group would be debuting under the name "Ampers&One". On the same day, Brian was revealed as the third member of the confirmed lineup.

On November 15, the group debuted with the single album Ampersand One and its lead single "On and On", with lyrics co-written by Kamden.