The Black Cats dropped to ninth in the Championship following their 1-1 draw with Millwall last weekend, making it just two wins from their last nine league matches and three games without victory.
Calling an end to Mowbray's 15-month reign at the Stadium of Light, Sunderland sacked the 60-year-old manager amid reports he had fallen out with the club's sporting director Kristjaan Speakman.
Reims manager Still, 31, has been identified as a possible managerial replacement, having impressed at the French side since he took on the role in 2022.
Will Still is reportedly on Sunderland's shortlist to take over as manager at the Stadium of Light
Tony Mowbray was sacked by the Championship club after Saturday's 1-1 draw with Millwall
During his breakout year as a manager, Still guided Reims through a 17-match unbeaten run. He was born in Belgium to English parents and began his managerial career at the age of just 24 in 2017.
According to the Guardian, Still is attracting interest from Sunderland because the club are keen to recruit a young manager. It is believed Ipswich boss Kieran McKenna and Nice assistant Julien Sable are also in the running for the Black Cats job.
McKenna, who has marshalled Ipswich to second in the Championship so far, is already attracting interest from a host of Premier League clubs.
Still sat down with Mail Sport's Daniel Matthews to talk about his 'dream' of one day returning to England as a manager.
Still, who guided Reims through a 17-match unbeaten run last season, is challenging for Champions League qualification this campaign with his side currently placed in fifth spot
Ipswich's Kieran McKenna is already attracting interest from a host of Premier League clubs