“Best” depends on your goals (budget, classes, 24/7 access, premium amenities, small-group training, travel access). Below are widely‑recognized gym chains around the world organized by category, with a short note on what each is best for and a recent size/scale figure so you can compare.

Largest/global franchise / convenience

• Anytime Fitness — 24/7 neighborhood franchise with extremely wide global access (good for travelers who want “go to any club”). Reported as one of the world’s largest gym franchises (several thousand clubs worldwide). (anytimefitness.com, axios.com)

Big low‑cost / high membership

• Planet Fitness — budget, “Judgement Free Zone” model; huge membership base and thousands of clubs (about 2,600–2,700 clubs and ~19–20M members as of year‑end 2024). Good if you want low monthly fees and basic equipment. (prnewswire.com)
• PureGym (UK/Europe) — no‑frills, low‑cost operator that’s rapidly expanded across Europe (hundreds of UK sites and several hundred total clubs after recent acquisitions; ~2.25M members end of 2024). Good for very low price and 24/7 access in many European cities. (corporate.puregym.com, healthclubmanagement.co.uk)
• Basic‑Fit (Europe) — large low‑cost chain across many European countries (1,500+ clubs across Europe as reported in H1‑2025). Good budget option in continental Europe. (marketscreener.com)

Large full‑service / mid‑to‑high end

• LA Fitness — big footprint in the U.S. with hundreds of clubs; full‑service (classes, pools at some sites). Good for families and people who want big facilities. (Estimates in mid‑hundreds of clubs). (scrapehero.com)
• Life Time — premium “athletic country club” model (resort‑style amenities, pools, courts); ~150–180+ centers in North America (premium pricing). Good if you want a luxury, family‑friendly facility with lots of amenities. (ir.lifetime.life)
• 24 Hour Fitness — large U.S. chain (hundreds of clubs; regionally strong in California) with multi‑tier memberships and many locations open long hours. Good if you want broad U.S. coverage and flexible access. (24hourfitness.com, scrapehero.com)

Heritage / bodybuilding

• Gold’s Gym — iconic brand with a large international footprint (several hundred international + many domestic locations after recent growth/rehabs). Good for serious lifters and strength training culture. (prnewswire.com)
• World Gym — long‑standing bodybuilding brand with a global franchise network (couple hundred locations worldwide). (en.wikipedia.org)

Boutique / class‑based chains (HIIT, studio classes)

• Orangetheory Fitness — heart‑rate‑based group training studios; rapid global expansion and ~1,300–1,500+ studios worldwide (strong group‑class model). Good if you like coached, interval classes with data tracking. (businesswire.com, orangetheory.com)
• F45 — functional HIIT group training studios; was one of the largest boutique concepts (industry reporting and company pages show ~1,500–2,000 studios globally though franchise counts have varied with recent restructuring). Good for 45‑minute structured HIIT classes. (f45training.com, en.wikipedia.org)
• Crunch Fitness — value + class variety; hundreds of clubs and millions of members (rapid expansion, many locations across the U.S. and some international markets). Good for low‑cost access to classes and fun studio options. (prnewswire.com, crunch.com)

24/7 small footprint / neighborhood

• Snap Fitness — 24/7 convenient neighborhood clubs and franchised model (large franchise footprint worldwide; many U.S. locations). Good for quick visits and flexible hours. (snapfitness.com, scrapehero.com)

Notes and tips

• Numbers above are from recent company reports and industry press releases (late‑2023 through 2025); chains open and close clubs frequently (acquisitions, bankruptcies, rebrands and franchise sales are common). Where I cited specific membership or location counts I noted the company/date — treat those as snapshots, not permanent totals. (prnewswire.com, corporate.puregym.com)
• “Best” depends on your priorities: price (Planet Fitness, PureGym, Basic‑Fit), travel/access (Anytime Fitness), premium experience/amenities (Equinox, Life Time), coached group classes (Orangetheory, F45), or serious strength culture (Gold’s, World Gym).
• If you want, I can narrow this to “best for: under $30/month”, “best for travelers (international pass)”, “best boutique chains”, or give top picks in a specific city or country.

If you want a tailored shortlist (e.g., best options near