News emerged on Wednesday evening of a move being imminent , and both Liverpool and Southampton confirmed the news on their official websites at 6pm.
The 26-year-old, also linked with a move to Manchester City and Chelsea in recent weeks, will make the switch between clubs when the transfer window opens on January 1.
Netherlands international Van Dijk is expected to cost the Reds around £75m, making him the most expensive defender of all time.
A statement on Liverpool’s official website read: “Liverpool Football Club can confirm they have reached an agreement with Southampton for the transfer of Virgil van Dijk.
“The Reds have agreed a deal with the South Coast club, and the player himself, that will see the 26-year-old defender move to Anfield when the transfer window re-opens on January 1, 2018.”
Van Dijk, who has been left out of the Saints’ squad in recent games, will wear the number four shirt at Anfield.