The former Bologna boss, who was sacked in January, will be unveiled by the Serie A giants on Friday after replacing Edy Reja at the Stadio Olimpico on a two-year deal
The Aquile endured a difficult 2013-14 campaign, finishing ninth and missing out on European qualification, and it was announced on Thursday that Reja would be leaving the club despite only arriving in January following the sacking of Vladimir Petkovic.
Rumours had circulated since the end of last season that the 68-year-old would step down from his role at the club after disappointing results and fostering a poor relationship with supporters and Lazio have ultimately chosen Pioli as his successor.
"Lazio announces that Stefano Pioli will be the new coach of the first team from July 1, 2014," read a statement on the club's official website.
"A press conference presentation is scheduled for [Friday] at 11:00BST."
Pioli was sacked by Bologna in January after leaving the Rossblu one point above bottom spot in Serie A.
His appointment came only hours after it was revealed that Reja had left his position as Biancocelesti president Claudio Lotito looks for the club to challenge for European qualification next term.