Virtanen, 21, is Hibernian’s fifth signing of the transfer window and joins from Finnish Premier Division outfit IFK Mariehamn, based in the Åland Islands.
The 6ft 5in ‘keeper has made seven appearances for Finland’s Under-21 squad, and has had spells with Åbo IFK and TPS.
Hibernian head coach Alan Stubbs said he was ‘delighted’ to have sealed a deal for Virtanen, adding: “Otso is someone we’ve been tracking for a while.
“He is a keeper with lots of potential that we’re looking forward to developing.
“I’m sure he’ll be another positive addition to the first team squad.”
Virtanen becomes the fifth Finn to turn out for Hibernian, after midfielder Jarkko Wiss, forwards Jonatan Johansson and Shefki Kuqi and former striker and manager Mixu Paatelainen.
Hibs have already signed Chris Dagnall, Kevin Thomson, Niklas Gunnarsson and Anthony Stokes in this window.