Clubs spent a record £430 million ($611 million, 492 million euros) last month -- nearly double the previous record of £225 million, according to accountancy firm Deloitte's.
Pierre-Emerick Aubameyang's arrival headlines major changes at Arsenal, Manchester United beat local rivals Manchester City to the signing of Alexis Sanchez and Virgil Van Dijk and Aymeric Laporte became the two most expensive defenders in history after joining Liverpool and City.
AFP Sport looks at the major talking points of the frenetic window.
Arsenal departed from their usual cautious transfer policy, bringing in Aubameyang (£56 million) and Henrikh Mkhitaryan from Manchester United in exchange for Sanchez, who had just six months left on his contract.
Mkhitaryan and Aubameyang will be looking to recreate the deadly partnership they formed in three years together at Dortmund, where the prolific Gabon striker netted 141 goals in 213 games, in a new-look frontline that raises questions over the future of Alexandre Lacazette, signed for a then club-record fee just six months ago.
Just as crucial to Arsenal's prospects was tying down playmaker Mesut Ozil to a bumper new three-and-a-half year contract on deadline day.
A fresh outlook on the field is reflected off it. The signing of two former Dortmund stars hints at wider changes at the club hot on the heels of the appointment of new chief scout Sven Mislintat, who also brought both players to the German giants in 2013.
Mislintat will soon be joined by former Barcelona director of football Raul Sanllehi as the club's new head of football relations, suggesting Arsene Wenger's grip on power may be weakening after more than two decades at the helm.
Conte's complaints at Chelsea
Chelsea benefited from the clear-out at Arsenal, signing Olivier Giroud to land the target man Antonio Conte has been chasing to add firepower to his stuttering forward line.
The French international, 31, split opinion in his five-and-a-half years with the Gunners, where he was capable of spectacular goals but struggled to convince Arsene Wenger he was worth a permanent starting berth.
However, he is exactly what Conte sought as an alternative to Alvaro Morata up front, with the out-of-favour Michy Batshuayi shipped out to Dortmund on loan to complete the Arsenal-Chelsea-Dortmund triangle of striker swaps.
Conte bemoaned his side's "disastrous" preparation for Wednesday's shock 3-0 home defeat to Bournemouth, blaming the transfer upheaval.
It was not his first complaint about not having a strong-enough influence on the club's transfer policy, increasing speculation he may not remain in charge at Stamford Bridge beyond the end of the season.
Moneybags Manchester clubs strengthen
United may not have spent a penny in transfer fees but committed to reportedly the biggest contract in English football history by tying down Sanchez for the next four-and-half-years.
Beating City to Sanchez's signature was a small crumb of comfort for the red side of Manchester, with Pep Guardiola's men romping towards the Premier League title, now 15 points clear of their fierce rivals.
City reinforced at the back with a club record signing of Laporte from Athletic Bilbao for £57 million, pushing their spending on defenders alone since Guardiola arrived 18 months ago to more than £200 million.
Crucially, both Sanchez and Laporte are free to play in the Champions League, with both sides of the Manchester divide eyeing European glory.
No panic at the bottom
The huge sums of television money on offer for survival in the Premier League has often seen those at the bottom more active than at the top in January.
However, that was not the case this month, with many relegation threatened sides refusing to panic-buy.
Despite slumping into the bottom three, Southampton were one of few sides to end January in the black after their windfall for van Dijk (£75 million), with Argentine striker Guido Carrillo's near £20 million move from Monaco their only major move.
Bottom-of-the-table West Brom have pinned their hopes of survival on a return to form for Daniel Sturridge after he sealed a six-month loan deal from Liverpool.
Newcastle United were also forced to turn to a flurry of last-minute loan deals for Kennedy, Islam Slimani and Martin Dubravka.