Not a chain but a very upscale marketing organisation. Members include world top-class hotels like some Mandarin Orientals (SFO, BKK, others), some Peninsula hotels (HKG, BKK), some Mexican Camino Real properties, most of the finest (mostly individual) European hotels, etc, etc. etc.
The organisation has not a frequent-flyer/miles/points-program of their own, but many of their individual members/properties have.
I got, years ago, a complimentary (life long) Leaders Club Card that allows some upgrade advantages and special treat.