In June 2021, Gkillas signed a five-year contract with Olympiacos, joining their senior men's water polo squad as a young international talent. Gkillas earned promotion from Greece's U20 squad to the men national team and was selected for the squad at the 2023 World Aquatics Championships in Fukuoka. He competed at the 2024 Summer Olympics in Paris, where Greece finished fifth. In April 2025, he played in the World Aquatics Men’s Water Polo World Cup gold-medal match versus Spain in
Podgorica, where Greece eventually got the silver medal. In July 2025, he competed in the World Championships held in Singapore, helping Greece national team to prevail in the bronze-medal game against Serbia. ==References==