Williamson retires having played 93 T20I matches for the Black Caps and having scored more than 2500 runs in the shortest format.
The New Zealand legend will continue to play Test and ODI cricket for the Kiwis, with Williamson's name a notable omission when the Black Caps named their T20I squad to face the West Indies later on Sunday.
Williamson's last T20I was at the ICC Men's T20 World Cup in 2024 against Papua New Guinea, and will not be considered for the Black Caps' T20 World Cup 2026 campaign in India and Sri Lanka.
Williamson made his T20I debut in 2011 and led the Black Caps on 75 occasions, taking them to two T20 World Cup semi-finals (2016 and 2022) and a final in 2021.
His innings of 85 in the 2021 decider against Australia remains the highest score by a captain in any edition of the Men's T20 World Cup.
The 35-year-old said the timing was right to take the step back.
“It’s something that I’ve loved being a part of for a long period of time and I’m so grateful for the memories and experiences,” Williamson said on Sunday.
“It’s the right time for myself and the team. It gives the team clarity for the series moving forward and ahead of their next major focus which is the T20 World Cup.
“There’s so much T20 talent there and the next period will be important to get cricket into these guys and get them ready for the World Cup.
“Mitch (Santner) is a brilliant captain and leader - he’s really come into his own with this team.
“It’s now their time to push the Black Caps forward in this format and I’ll be supporting from afar.”
