Here are three highly regarded luxury wellness-retreat options in Sri Lanka, with what makes each special, where they are, who they suit best, and practical notes (best time to travel). I’ve included sources so you can check current programmes, prices and availability.

1. Santani Wellness Resort — Kandy (hill country)

• Why go: Purpose-built luxury wellness retreat focused on personalised Ayurveda, detox, yoga and nature-led restoration; minimalist architecture, thermal spa suite and strong emphasis on digital detox and long-form programmes. (santani.com)
• Suits: Guests wanting an intimate, design-forward, medically supervised wellness reset (multi‑day Ayurveda/detox/yoga).
• Practical: Located in the central highlands (cooler climate, former tea estate). Typical stays are 7+ nights for deeper programmes; transfers from Colombo take ~3–4 hours. (wellnessholidayboutique.com)

2. Anantara Peace Haven Tangalle — South coast (beach)

• Why go: Luxury beach resort that offers structured Ayurvedic wellness programmes (Inner Harmony, Deep Sleep, Detox, 5–7+ day packages) combined with high-end resort comforts and spa therapies overseen by resident Ayurvedic doctors. Some seven‑night packages include personalised consultations, life coaching and nutrition coaching. (Anantara.com)
• Suits: Travellers who want classic resort luxury and a formal Ayurvedic programme without giving up beachfront villas and resort amenities.
• Practical: South-coast location (Tangalle/Madurai area). Example published starting-price reference for multi-night Ayurvedic packages was reported around mid‑four figures USD — check current rates and seasonal offers directly with the resort or an agent. (luxurytraveladvisor.com)

3. Barberyn Ayurveda Resorts (Reef / Beach / Sands) — south‑west coast (Beruwala, Weligama, Bentota)

• Why go: Long-established, authentic Ayurvedic centres specialising in traditional Panchakarma and medically supervised regimens; family‑run, strong clinical focus and day-to-day Ayurvedic cuisine and treatment schedules. Often ranked for value and authenticity rather than ultra‑minimalist luxury. (barberynresorts.com)
• Suits: Guests seeking a genuine, medically rigorous Ayurveda experience (detox, panchakarma) at more modest prices than some of the ultra‑luxury properties.
• Practical: Multiple properties on the south coast; programmes commonly run 7–14+ nights for effective results. Recent guest reviews and specialist-wellness sites report very high treatment quality. (wellnessloka.com)

Best months and weather (planning note)

• For south and west coast beach properties (Anantara, Barberyn): the main dry season is generally November–April — this is the most reliable period for beach and outdoor activities. For hill-country retreats (Santani), the climate is cooler year‑round but best travel windows align with dry months. (Sri Lanka’s monsoon patterns vary by coast and season; check exact travel dates.) (thetimes.co.uk)

Quick booking tips

• Plan 7+ nights for meaningful Ayurveda/detox programmes.
• Confirm whether a resident Ayurvedic doctor is included in your package and whether prescribed herbal medicines or special diets are covered.
• Ask about airport transfers (private transfers can be long if coming from Colombo), digital‑detox policies, and any pre-arrival health forms. (santani.com)

If you want, I can:

• Narrow choices by region (beach vs hill), programme type (Panchakarma vs yoga/detox vs rest & spa), or budget; or
• Check current availability and sample package prices for specific dates (I’ll check live rates and give quotes/links).