Lee Hong-gi (이홍기) is a South Korean singer, actor, and songwriter best known as the lead vocalist of the rock band F.T. Island. Recognized for his powerful and emotive voice, Hong-gi has been a central figure in the Korean rock and pop scene since the mid-2000s. Alongside his music career, he has appeared in several popular Korean dramas, further solidifying his status as a versatile entertainer.

Lee Hong-gi collaborated with ONE OK ROCK behind the scenes as a co-composer on two F.T. Island tracks: "Primavera" (released April 17, 2015) and "My Birthday" (released May 13, 2015). Both songs were featured on F.T. Island's Japanese releases and showcase a fusion of J-rock and K-rock influences. While Taka from ONE OK ROCK did not perform on these songs, he and Hong-gi worked together on the songwriting process, highlighting the creative synergy between the two bands.