The new deal will cover the Vitality Blast for the next four years, as well as England men's and women's home T20 series for two years.
NatWest signed a four-year contract in 2014 to support domestic T20, before widening its agreement with the ECB.
The new partnership will give Vitality full competition naming rights, in-ground advertising and hospitality rights as well as access to England players.
The insurer has been an official partner of the ECB since 2013 and counts England Test captain Joe Root as one of its ambassadors. Beyond cricket, Vitality’s sponsorship portfolio includes a variety of sports including football, rugby, hockey, netball and run events.
ECB commercial director, Rob Calder, said: “We’re excited to be working with a partner who shares our enthusiasm and passion for T20 cricket. It’s the fastest growing format of the game, an integral part of ECB’s long-term strategy and has a critical role to play in bringing new people to the sport.
“Vitality is an established brand in the sports marketplace with a proven track record of using sponsorship successfully to grow fan-bases and improve participation levels. They’re a natural fit for a partnership to drive interest and engagement in all our different T20 competitions at every level.”
Neville Koopowitz, CEO of Vitality, added: “We're delighted to be partnering with the ECB for T20 cricket. T20 is a brilliant innovation that's revolutionising the sport around the world.
“This new sponsorship aligns with our own vibrant brand and fits with our desire to increase awareness and engagement among families and across all levels of the game while at the same time telling more people about Vitality."