24 Hour Fitness
You won't have to wait to use an elliptical at this spacious gym, which boasts plenty of cardio equipment, along with a weight room and free Wi-Fi. If you're heading out after your late-night workout, freshen up with a selection of gratis toiletries, including razors, mouthwash and hair products. 225 Fifth Ave between 26th and 27th Sts (212-271-1002, 24hourfitness.com). Daily 24hrs. Memberships start at $85 per month.
RECOMMENDED: Fitness guide to NYC
LA Fitness Elite
In addition to extended hours, this branch of the national chain offers relatively inexpensive memberships—plans start at $35 per month. You'll get access to the club's extensive amenities, including racquetball and basketball courts, a swimming pool and a sauna (the latter two close a half hour before the gym itself). 145 E Service Rd between Beresford and Wild Aves, Staten Island (718-761-5606, lafitness.com). Mon--Thu 4am--midnight; Fri 4am--10pm; Sat, Sun 6am--7pm. Memberships start at $35 per month.
Rock Health & Fitness Club
Go beyond the treadmill at this Queens gym, which features a regulation-size boxing ring and a 30-foot-high climbing wall, both of which are open all day (and all night on weekdays). But never fear, cardio fiends: There's also an abundance of machines on which you can work up a sweat, along with brand-new Kinesis equipment. 22-15 31st St between Ditmars Blvd and 23rd Ave, Astoria, Queens (718-204-1400, therockhealthandfitness.com). Mon--Fri 24hrs, Sat 7am--9pm, Sun 7am--8pm. Memberships start at $78 per month.
Zoom through a sweat session in the weight or cardio room before heading to the lounge, where you can kick back in front of the fireplace in a swanky massage chair. 1385 Commerce Ave between Butler Pl and Halsey St, Bronx (718-823-2323, starfitnessnewyork.com). Mon--Fri 24hrs; Sat 7am--7pm, Sun 7am--5pm.
Harbor Fitness Center
This Park Slope gym offers a multitude of 24/7 amenities: After pushing yourself on a StairMaster or in the weight room, stop by the juice bar for a smoothie, then cleanse your pores in the sauna. 191 15th St between Fourth and Fifth Aves, Park Slope, Brooklyn (347-497-6148, harborfitness.com). Mon--Fri 24hrs; Sat, Sun 7am--9pm. Memberships start at $59 per month.