Here are top beach resorts across Sri Lanka (by region), with a short note on why each is special and a source you can check:

South / Southwest coast

• Cape Weligama (Weligama) — cliff-top villas, dramatic infinity pool and excellent sunsets; top luxury pick on the south coast. (livingmagazine.lk)
• Amanwella (Tangalle) — intimate Aman property with a secluded crescent beach and large private suites; great for privacy and wellness. (cntraveller.com)
• Wild Coast Tented Lodge (near Yala) — luxury tented lodge where jungle meets beach (excellent for combining beach time with safari). (resplendentceylon.com)
• The Fortress Resort & Spa (Koggala/Galle area) — family‑friendly luxury with good facilities, spa and easy access to Galle. (slh.com)

West coast / Bentota area

• Cinnamon Bentota Beach (Bentota) — iconic Geoffrey Bawa‑designed resort, long beach and lots of water‑sport options. (cinnamonhotels.com)
• Taj / Vivanta by Taj (Bentota) — well‑known seafront resort with strong service and cliffside views of Bentota beach. (oyster.com)
• Jetwing Saman Villas (Bentota/Aturuwella) — boutique, romantic villas on a rocky promontory (classic boutique option). (en.wikipedia.org)

East coast (best May–October)

• Trinco Blu by Cinnamon (Trincomalee / Nilaveli) — one of the larger, reliable beachfront hotels on the northeast; good base for Pigeon Island snorkeling. (cinnamonhotels.com)
• Uga Bay / Uga Escapes (Pasikuda / Kalkudah) — upscale beachfront option on the shallow, calm Pasikuda waters (excellent for families and snorkeling). (ugaescapes.com)
• Karpaha Sands (Pasikuda / Kalkudah) — boutique beachfront property on a long, shallow bay (a quieter, design-forward choice). (travelmyth.ie)

East / surf (Arugam Bay)

• Jetwing Surf (Pottuvil / Arugam Bay) — modern beachfront cabanas close to the Arugam Bay surf breaks (great for surfers and relaxed beach life). (jetwinghotels.com)

North‑west / kitesurf & dolphins

• Dolphin Beach (Alankuda / Kalpitiya) — small eco/tent resorts and kite/dolphin‑watching base on the Kalpitiya peninsula. (en.wikipedia.org)

A few practical notes

• Best time: south & west coast = November–April; east coast = May–October (monsoon patterns mean you should pick the coast that’s in season). (lonelyplanet.com)
• How to get there: most international arrivals fly into Bandaranaike Intl (Colombo) and then transfer by car, train or short domestic flight depending on the resort. Luxury properties commonly arrange transfers and domestic flights. (Check each resort’s site/concierge for the current transfer options.)

If you’d like, I can:

• Narrow this to resorts in a single region (south / east / Bentota / Arugam Bay), or
• Give price ranges, typical room types, and sample itineraries (3–7 nights) for any 2–3 resorts you pick.