The 17-year-old attacking midfielder will join the Reds' Academy ranks ahead of the 2027-28 season, after a move to bring him to the club was completed.
Martinez starred for Colombia as they were winners of the U17 South American Championship in April.
He featured in all six of his country's games at the tournament and registered three assists, including one each in the 3-0 semi-final defeat of Brazil and 4-0 final victory over Argentina.
