Arsenal have agreed deals with Chelsea for Brazilian centre-back David Luiz and Celtic for Scottish left-back Kieran Tierney, sources have told ESPN FC.
Both players are expected to be at Arsenal's training ground in London Colney on Thursday to pass their medicals and sign their contracts.
Luiz will sign a two-year deal and will cost £8 million while Tierney will put pen to paper on a five-year contract. Celtic will receive £25m, which will be spread over the length of the deal.
Arsenal were actively looking for a centre-back following the departure of Laurent Koscielny, who left to join Bordeaux earlier in the transfer window and looked at various options before the possibility of signing David Luiz became available.