Lazio have completed the signing of Pedro Rodriguez from AS Roma in what is the first transfer between the Italian capital's cross-city rivals in 40 years.
Pedro signed a three-year deal with Roma last summer after arriving on a free transfer from Chelsea, but was deemed surplus to requirements by new boss Jose Mourinho and was left out of the team's pre-season preparations.
Lazio manager Maurizio Sarri was keen to reunite with Pedro after having coached him at Chelsea in the 2018/19 season.
Roma were keen to offload the forward to a foreign club but would have lost out on around €3.5m due to Italian state laws on tax benefits.
Lazio will not have to pay Roma any transfer fee but will take on the Spaniard's current wages of around €4m per year pre-tax, plus bonuses depending on team performances next season.
Over the years, a host of different players wore both jerseys - including Aleksandar Kolarov, Sinisa Mihajlovic, and Angelo Peruzzi - but direct transfers between the two clubs have been very rare.
The last transfer between the two capital rivals took place in 1981 when Carlo Perrone swapped Lazio for Roma before returning to his former club the following year.