Gunter has been a Welsh international since under-17 level and holds the record as the second youngest debutant for the under-21 team. He made his full international debut in 2007. He was part of the Wales squad that reached the semi-finals at UEFA Euro 2016, also featuring at Euro 2020. In 2017 he was named Welsh Footballer of the Year. He beat Neville Southall's record of 92 caps in 2018, and in 2021 became the first Welshman to earn 100 caps.