Deelen Air Base (Dutch: Luchtmachtbasis Deelen or Vliegbasis Deelen) is a military air base in the Netherlands in the province of Gelderland. Though once an active air base, it is now mostly used as a helicopter training site. Being one of the oldest airports in the Netherlands, many buildings on the airfield are now listed as monuments.
There was less need for the air base after the end of the cold war and in 1995 it was closed as such. The top layer of the runway was removed making it no longer suitable for landings by heavy aircraft. Its designation was downgraded to Military Aviation Site Deelen (Dutch: Militair Luchtvaart Terrein Deelen). However, it remained in use as a military site for helicopter training and for that reason is frequently visited by various military helicopters, such as the Boeing AH-64 Apache, Boeing CH-47 Chinook and Eurocopter AS532 Cougar. None of these helicopters are based at Deelen however and for that reason the base is only fully operational when exercises take place. The closure of Soesterberg Air Base resulted in a lot more helicopter movements at Gilze-Rijen Air Base, and in order to reduce traffic there it was decided to use Deelen more often as a training site. To facilitate this it was decided to resurface the runway and to create a slope for helicopters to practice sloped landings on. The increased importance of Deelen resulted in it once again receiving the designation of Air Base (Dutch: Vliegbasis).
There is also glider activity on the field and very nearby there is a second aerodrome used almost exclusively by gliders, Terlet Airfield.