Following the departure of Enrico Chiesa for Siena, Lazio boss Roberto Mancini was looking to bolster his attacking options.
Muzzi had been linked with a switch to the Italian capital several times but has now finally penned a three-year deal at Stadio Olimpico.
The 31-year-old has spent time at fierce Roman rivals Roma but is now looking to bring his experience to the blue half of the Eternal City.
Despite this, Muzzi has always said he was a lifelong Lazio fan and had been desperate for the move.
Lazio have, meanwhile, allowed midfield man Christian Manfredini to secure a loan move to Fiorentina.
The former Chievo winger is still not in Mancini's plans after returning from a loan spell at Spanish side Osasuna, and will now move to Fiorentina.
Lazio are also still in the hunt for Real Madrid's Santiago Solari, and have not given hope of landing the Argentinian.
The club are desperate to lure Solari to Italy and have made an improved offer to the player and are now sweating on his reply.
