The 34-year-old former Spain international is the first player to directly move between either club for 36 years.
Pedro only joined Roma from Chelsea in the summer of 2020 after spending five years at Stamford Bridge, winning the FA Cup, Premier League and Europa League.
Pedro made 40 appearances across all competitions for Roma last season, scoring five goals, as the Giallorossi finished seventh in Serie A.
The arrival of Jose Mourinho, who incidentally signed Pedro for Chelsea, at Roma this summer has pushed the former Barcelona forward down the pecking order.
Pedro was not even included in Roma’s squad for their pre-season preparations and opted to release him just one year into the three-year contract he signed when moving to Italy.
Pedro has been given the number nine jersey at Lazio and will be reunited with Maurizio Sarri, who coached him at Chelsea in the 2018/2019 season.
Pedro won 65 caps for the Spain national team, scoring 17 goals and was part of the squads that won the 2010 FIFA World Cup in South Africa and the 2012 European Championship.
He also won five La Liga titles and three Champions League trophies among numerous other honours during his time with Barcelona.
