The 36-year-old winger, who has been capped 93 times for the Republic of Ireland, has agreed to reunite with his former Sunderland boss Lee Johnson and he will now head off with his new team-mates on their pre-season trip to Portugal on Sunday.
The winger, whose contract with the Black Cats officially expires at the end of this month, made over 200 appearances for Celtic before joining Spartak Moscow.
He also signed for Everton, going out on loan to Sheffield Wednesday and Preston North End before making a permanent switch to the Stadium of Light.
After being sent out on loan to Charlton Athletic, he returned to Sunderland and made his first appearance in over a year under the new boss, Johnson, and went on to contribute eight assists in his first 12 games for his gaffer.
The pair went on to establish a strong working relationship as McGeady was named in the 2020/21 EFL League One Team of the Season after contributing six goals and 17 assists from out wide.
The guile and experience on the flanks is what Johnson is now hoping he can bring to the Leith side as they looked to improve on last season.
"He will bring skill, experience and gravitas to our team,” said the delighted Hibs manager. “Aiden is a top player, he has had a fantastic career to date and we aim to extend and accentuate his abilities within the blend of our new-look squad.
“We will also look to utilise Aiden’s fantastic leadership qualities to help guide and get the best out of our young forward players.”
The club’s seventh first team signing of the summer transfer window , he follows David Marshall, Nohan Kenneh, Rocky Bushiri, Lewis Miller, Momodou Bojang and Jair Tavares in the door, with at least another centre-half and another striker expected to join them.
Head of recruitment Ian Gordon said: “Aiden will bring an excellent blend of experience and top-class quality to our side.
"He has played at the very top level during his career and will help raise our standards going forward.”