The game marks the full cross-platform expansion of the 20-year old franchise across mobile and PC. Players who subscribe on mobile can now play the full game on the desktop version and vice-versa.
Subscribers gain eight additional skills, over 120 extra quests and access to the entire world map compared to free players.
In terms of the mobile release, over 1.8 million mobile gamers pre-registered for the launch and to celebrate the mobile launch, new players can claim a free 7-day trial.
Pre-registered players will also receive five exclusive cosmetic rewards, including hairstyle, teleport device, sword, pet and the top tier prize which includes the Crux Eqal armour and delivers a 50 per cent XP boost across a seven-day period.
"We believe in taking our living games to wherever our players want them and, with the mobile editions offering cross-platform play with PC, players can now continue their adventures when they’re away from their desktop screens," commented Jagex CEO Phil Mansell.
"The arrival of RuneScape on mobile is testament to our commitment to the continued growth of both titles as multi-platform living games.”
RuneScape has racked up almost 300 million registered accounts and Jagex says is currently experiencing its "peak popularity".
Old School RuneScape was released on mobile in 2018 and has been installed more than 13 million times to date.
Runescape also recently announced a slew of new hires, including execs from PlayStation, Bethesda and Insomniac Games.