Arsenal have completed the signing of David Luiz from Chelsea on a two-year deal for a fee of £8m.
The Brazilian centre-back, who made 248 appearances for Chelsea across two spells with the club, underwent his medical on Deadline Day after the two sides agreed a fee.
Luiz trained away from the rest of Frank Lampard's squad on Wednesday after indicating he wanted to leave the club.
"David has huge experience and I look forward to working with him again," Arsenal head coach Unai Emery said.
"He is a well-known player and adds to our defensive strength."
The 32-year-old is Arsenal's second Deadline Day signing after they completed a £25m deal for left-back Kieran Tierney from Celtic.
Arsenal had been left short at centre-back after the departure of former captain Laurent Koscielny, who shocked the club by demanding a transfer with a year left on his contract.
Luiz began his first spell at Chelsea in 2011, before returning to Stamford Bridge in 2016 after a two-year spell with Paris Saint-Germain.