Bosses said the state-of-the-art facility has been transformed to cater for our world class gymnasts and the local community.
The all-new equipment has been made possible thanks to funding from Sport England, and support from Serco and Gymnova.
Jane Allen MBE, British Gymnastics CEO, said: "We are delighted to be welcoming back our gymnasts into the new gym which I am sure they will agree looks absolutely fantastic. Thanks to our performance teams and the input of our creative staff, we have one of the best training facilities in the world which compliments the standard of our world class programme.
"British Gymnastics is extremely grateful for the fantastic support from Sport England, Serco and Gymnova for making this possible. I look forward to seeing more of our gymnasts making use of the new facility in the coming months as our preparations step up towards Tokyo."
Both Kings Hall and Princess Royal Hall were closed in October 2019 when work began. Doors have reopened this week, with the gym being used for the first time by the senior men’s artistic squad as they take part in their opening training camp of the year, as well as a number of community clubs.
The gym has undertaken a huge transformation in that time.
Olympic medallists, Beth Tweddle MBE, Louis Smith MBE, Max Whitlock MBE, Amy Tinkler and Nile Wilson, and the 2012 Olympic men’s team that won a historic bronze medal have all been recognised as part of the rebranding.
Charles Johnston, planning and national centres property director at Sport England, said: "We’re delighted to be funding the update and refurbishment of the gymnastics centre at Lilleshall to incorporate the latest world class facilities.
"These will not only assist our elite gymnasts but also support future talent and grassroots programmes - enabling British Gymnastics to drive community participation together with expanded coach development and education programmes.
"Congratulations to all those involved in delivering such an exciting development."
The history of the sport is also recognised with a timeline of historic firsts now visible in the viewing gallery, pieced together using images that predate the formation of British Gymnastics in 1888.
The gym floor has taken on a new look thanks to the addition of brand new equipment, supplied and fitted by Gymnova.
Steve Nelson, Serco Leisure’s partnership director (national centres) said: "It’s great to see this project completed. These new facilities are first class, providing somewhere for elite athletes to train and prepare for major competitions, but also a place for the local community to use and benefit from.
"We’re very proud to be a part of this exciting new chapter for gymnastics at Lilleshall National Sports Centre.”
Speaking after seeing the gym for the first time, James Hall, men’s senior British all-around champion, said: "It’s like walking in to a completely different place. I’ve been coming to Lilleshall for nearly 15 years and it’s amazing to see the brand new equipment and a completely new layout is really exciting.
"It’s all state-of-the-art. It’s amazing. It’s going to give us the best chance for the Olympic Games later this year."