The 40-year-old will assume the role of the FA's Senior Manager – Women Referees from September, where she will oversee the growth and development of women referees across England while helping create a stronger pathway into elite-level football.
Massey-Ellis leaves behind a distinguished officiating career that saw her become one of the most recognisable assistant referees in English football.
She made history in 2010 by becoming only the second female assistant referee to officiate in the Premier League and went on to take charge of more than 150 top-flight matches.
Her list of achievements also includes officiating five Women's FA Cup finals and becoming the first female assistant referee appointed to the Community Shield.
In 2021, she broke another barrier by becoming the first woman to be involved in a men's FA Cup final after serving as an assistant video assistant referee (AVAR). She later worked as an AVAR during the 2025 Carabao Cup final.
On the international stage, Massey-Ellis officiated at four UEFA Women's European Championships, two FIFA Women's World Cups and the 2018 UEFA Women's Champions League final.
She also made history in 2019 as the first English woman to officiate in a men's European club competition when she served as an assistant referee in a UEFA Europa League fixture.
Recognised for her contributions to the sport, Massey-Ellis was awarded an MBE for services to football.
Reflecting on her decision to step away from officiating, she said her commitment to football remains as strong as ever despite leaving the touchline.
"Although I am stepping away from the touchline, I am not stepping away from football.
"If my journey has helped change perceptions, open doors or inspire even one young person to believe they belong in the game, then I will consider that one of my greatest achievements.
"As I prepare for one final walk onto the pitch, I leave with nothing but gratitude. It has been the greatest honour to serve the game I love and represent English officiating."
Paying tribute to her career, Chief Refereeing Officer Howard Webb described Massey-Ellis as a pioneering figure whose influence would extend well beyond her years on the field.
"Sian has done us proud time and time again — domestically and on the international stage, breaking multiple barriers and setting the standard for those coming through in her footsteps."
Her appointment to the Football Association is expected to strengthen efforts to increase the number of women progressing through the refereeing ranks, ensuring her impact on the game continues long after her final match.