He will lead the side in the upcoming World Championship Division II Group A tournament in Tallinn, Estonia.
Kirk, 19, was headhunted in the 2018 draft by Arizona Coyotes, the first player born and trained in England to be selected into the world's top flight.
He is currently playing with the Peterborough Petes of the Ontario Hockey League after a brief return over the Christmas period to see family and friends.
Jordan Kelsall and Chad Smith will be his alternate captains.
GB meet hosts Estonia, as well as Korea, Lithuania, Romania and Spain, from 13th to 19th January at the Tondiraba Ice Hall.
Head coach, Slava Koulikov, said: "I think we have chosen a great leadership team and I have no doubt they will do a fantastic job.
"But it was a tough choice as there were many candidates who could have undertaken the roles.
"There is a great spirit in the camp at the moment and everyone is focused on the opening game against Lithuania."
All of GB U20s’ World Championship games will be shown on free-to-air television in the UK on FreeSports - and they begin their tournament against Lithuania tomorrow.
FreeSports is available free on Sky Channel 422, Virgin Media Channel 553, on Channel 64 on Freeview and BT and on Freesat Channel 252.
Great Britain U20s World Championship schedule (all face-offs listed as UK time)
Sunday 13th January: GB U20s v Lithuania U20s – 6pm LIVE
Monday 14th January: Korea U20s v GB U20s – 2:30pm LIVE
Wednesday 16th January: GB U20s v Estonia U20s – 6pm (Delayed FreeSports coverage at 10:30pm after live EIHL game)
Thursday 17th January: Romania U20s v GB U20s – 2:30pm LIVE
Saturday 19th January: GB U20s v Spain U20s – 11am LIVE