The 22-year-old was a prime target of Manchester United last summer, and links with Erik ten Hag's side naturally re-emerged when he was spotted at Wembley to witness the Red Devils lose 2-1 to Manchester City.
However, having been seduced by Mikel Arteta's Arsenal project, Timber has opted for the Emirates over Old Trafford, and the defender is expected to undergo his medical in due course after the two clubs shook hands on a fee.
Here, Sports Mole takes a look at which shirt numbers could be available to Timber ahead of his arrival in North London.
While Timber found success as a centre-back last season, the Netherlands international is equally adept on the right-hand side of a back four, and he is expected to occupy that role in the red and white of Arsenal.
Given Timber's exploits out wide, it has come as little surprise to see the Dutchman wear the right-back's traditional number two jersey for both club and country, having donned that shirt for Ajax since the start of the 2021-22 season.
Timber has also been the Netherlands' number two for the past three years, and with Hector Bellerin ending his long association with Arsenal last summer, the Gunners' '2' is currently awaiting its next taker.
It would certainly be a shock not to see Timber inherit the '2' in North London, where he would follow in the footsteps of Bellerin, Mathieu Debuchy, Abou Diaby and club legend Lee Dixon, who was in possession of the shirt for 15 years between 1987 and 2022.
However, should the number two become unavailable for any reason, Timber could easily earn the number three shirt if its current occupier Kieran Tierney completes an expected move away from the Emirates in the coming weeks.
While normally reserved for left-backs, the '3' has also been worn by Dixon and Bacary Sagna in North London, and Timber did sport that number at various levels in Ajax's youth system.
Before he became number two for both Ajax and the Netherlands, Timber started out as the '41' for the Amsterdam giants, but fellow new arrival Declan Rice has coincidentally sported that shirt throughout his senior career and is expected to continue with the unconventional number on his back.
The 22-year-old made his Netherlands debut in the number 25, which was worn by right-back Carl Jenkinson for several years at Arsenal, but the long-serving Mohamed Elneny has had a firm grip on that shirt since 2021.
Should current right-back Cedric Soares depart in the coming weeks, the '17' that Timber wore for Ajax's Under-19s would also become vacant, but one can expect the 22-year-old to immediately grab the '2' with both hands.