The 29-year-old singer and actor said Friday that he will enlist in the South Korean military next month.
All able-bodied South Korean men are required to serve two to three years in the military, a legacy of the Korean War of the 1950s.
Rain, whose real name is Jung Ji-hoon, said on his website that he hopes to come back "more mature."
He said: "I'll serve faithfully and diligently."
One of Asia's most popular stars, Rain made his Hollywood film debut in "Speed Racer" in 2008 and appeared in "Ninja Assassin" the following year.