The January transfer window closes in England and Scotland at 23:00 GMT on Wednesday, 31 January - as it does in France, Germany, Italy and Spain. Portugal's window closes on 2 February.
Keep up to date with all of the confirmed deals in our list below.
Signings confirmed between September and December can be found on our previous transfer page.
For all the latest rumours check out the gossip page and, for all the manager ins and outs, see the our list of current bosses.
1 January
Football League
Manny Onariase [Rotherham - Cheltenham] Loan
Pre-arranged deals that went through this month
Premier League
Viktor Gyokeres [IF Brommapojkarna - Brighton] Undisclosed
Adrien Silva [Sporting Lisbon - Leicester] £22m
Virgil van Dijk [Southampton - Liverpool] £75m
Scottish Premiership
Marvin Compper [RB Leipzig - Celtic] £1m
Football League
Josh Barrett [Reading - Coventry] Loan
Dayle Grubb [Weston-super-Mare - Forest Green] Undisclosed
Emiliano Marcondes [Nordsjaelland - Brentford] Undisclosed
Liam Noble [Forest Green - Notts County] Free
Alex Whittle [York - Forest Green] Free
International
Diego Costa [Chelsea - Atletico Madrid] Undisclosed
The page covers signings by Premier League, Championship and Scottish Premiership clubs, along with selected deals from overseas and the Scottish Championship.