Hair Party 24 Hours.   (Photo: Courtesy of Hair Party 24 Hours)

Red Market Salon
32 Gansevoort St., nr. Hudson St.; 212-929-9600
This bright, 2,400-square-foot loft in a commercial walk-up is helmed by two Fekkai alums. The salon houses six stylists, a small bar stocked with free wine, products by Davines and Phyto, and a sound system manned regularly by local D.J.’s; you can get a blow-dry and a buzz till 10 p.m.

Homme Spa
465 Lexington Ave., nr. 45th St.; 212-983-0033
This massive, 15,000-square-foot pampering spot is open till 3 a.m. on weeknights and midnight on weekends. Hot-towel massages and Dermalogica facials are signatures, but the place also encompasses a full-service barbershop and couples' rooms with Jacuzzis.

Hair Party 24 Hours
76 Madison Ave., at 28th St.; 212-213-0057
This Seoul-based chain offers a full pleather-bound menu of services 24 hours a day. The offerings include mani-pedis, waxing, massages, facials, cuts, coloring, makeup application, and even eyelash extensions. Conventional daytime hours are still the busiest, but deals are offered for appointments between 6 a.m. and noon.

Cleo II Spa
258 Third Ave., at 21st St.; 212-260-0600
This casual Gramercy-area nail salon serves customers until midnight every night except Sunday. The mainly Korean and Nepalese staff apply all-natural creams from Switzerland, and more than 350 Opi and Essie polish colors are on offer.

Osaka Health Spa
50 W. 56th St., second fl., nr. Sixth Ave.; 212-956-3422
One of the city’s best one-hour Shiatsu massages is at Osaka 56, which stays open until 2 a.m. Monday through Saturday. Before treatments, many opt for a complimentary hot-cold hydrotherapy ritual using the spa’s steam room, sauna, and ice-cold baths.