Creative Assembly's RTS sequel is already available in boxes at retail, and now joins a growing contingent of titles available to purchase and download from Valve's Steam service.
The game will only be available to buy if you're in the US, and the move to Steam actually makes the game available on two digital distribution platform - the other being Direct2Drive.
SEGA of America boss Simon Jeffery said he was pleased to get the game "quickly and easily into the hands of hungry fans everywhere."
SEGA has previously digitally distributed Alexander, the Rome: Total War expansion, and the move to Steam follows that of several other publishers who have been won over by Valve's service.
Medieval II is available on Steam from today and will set you back $49.95.