Greece international Kostas Manolas has signed for Napoli from rivals Roma, the Serie A club announced on Saturday.
Napoli posted a picture of the 28-year-old on their Twitter account, with the message "Welcome Manolas!" shortly after club president Aurelio De Laurentiis had tweeted "Welcome Kostas!" in Italian.
The centre-back spent five years in the Italian capital, and moved to Carlo Ancelotti's side for a reported fee of 36 million euros ($40.6 million).
Manolas had been a key player for a Roma team that had in recent years consistently finished in the top places in Serie A, but he did not win a trophy in the Eternal City as Juventus have hoovered up the domestic honours in the last eight years.
Manolas played more than 200 times for Roma and will be best remembered for the goal that sent Roma through to the semi-finals of the 2018 Champions League as they completed a remarkable comeback from a 4-1 first-leg deficit against Barcelona to make the last four.
However, last year Roma missed out on elite European football after finishing sixth, while Napoli comfortably took second behind Juve, ensuring their place in the group stage of next year's competition.
Napoli and Roma have a fierce rivalry that has frequently spilled over into serious violence between supporters.
In 2014, Napoli fan Ciro Esposito died after being shot by a Roma supporter ahead of that year's Coppa Italia final, won at Rome's Stadio Olimpico by Napoli against Fiorentina.