After a horrendous 5-0 loss at Ipswich Town on Friday night, the Blades are at the bottom of the Championship on 0 points.
Selles was sacked last weekend after just five games, much to the relief of supporters.
The former Blades boss will manage the club for a third time after his side lost in the Championship play-off final at Wembley to Sunderland, who are enjoying life in the Premier League.
Wilder has two promotions with United to his name and has the task of turning the club around ahead of this Saturday’s clash with Charlton Athletic.
A message from the board of directors at United was shared on the club website as the decision to bring Wilder back was explained:
"Following a difficult start to the season, the board felt it necessary to make a change in order to stabilise performances and strengthen our push for promotion. While the adoption of a different style of play was pursued with ambition, results have clearly not met expectations.
"Chris Wilder returns with proven leadership and an unparalleled understanding of Sheffield United. We are confident he is the right person to restore momentum, unite the squad and supporters, and deliver the results necessary to achieve our objectives this season.
"We would like to thank Ruben Selles for his hard work and professionalism during his time at the club. Responsibility for recent results lies with us as owners, and we remain fully committed to supporting the team and pursuing promotion."
Wilder is a boyhood fan of United and will attempt to snatch three points at the weekend as he aims to revive what has been a disastrous start to the season so far.