Here are some of the most reputable real‑estate developers/builders active in Kolkata (widely recognised for project quality, scale and track record). I’ve included a short note on what each is known for and citations you can check.

• Ambuja Neotia — strong local brand, focus on high‑quality, sustainable and mixed‑use developments (projects in New Town, South Kolkata). (rivirtual.in)
• Merlin Group — major Kolkata developer noted for premium residential towers and modern amenities across the city. (rivirtual.in)
• PS Group (PS Projects) — known for large residential townships and engineered design emphasis in Greater Kolkata and New Town. (rivirtual.in)
• Srijan Realty / Srijan Group — a significant regional player with large residential and mixed‑use projects in and around Kolkata. (nobroker.in)
• Godrej Properties — national developer with Kolkata projects that emphasise sustainability and branded construction standards. (nobroker.in)
• Shriram Properties — active in affordable and mid‑segment housing around Kolkata and peripheral townships. (nobroker.in)
• Unitech / Uniworld projects — large township developments (Uniworld City in New Town is a landmark project). (en.wikipedia.org)
• Siddha Group / Sobha / other national builders — several national builders (Siddha, Sobha, DLF and others) have notable projects or presence in Kolkata; good to consider for branded offerings. (nobroker.in)

Notes on picking a builder (important when comparing offers)

• Check RERA registration and project timelines for the specific project (possession history matters).
• Review recent customer feedback, delivery record (on‑time completion), and bank approvals for the project.
• Consider location (New Town, Salt Lake, Southern suburbs, Howrah) — infrastructure and resale value vary a lot by micro‑location.
• Compare carpet area, maintenance estimates, warranty/defect liability and developer compensation policies for delays.

If you want, I can:

• Narrow this to “best for luxury”, “best for budget/affordable”, or “best in New Town / South Kolkata”; or
• Pull current project listings, RERA numbers and recent customer reviews for 3–5 of these builders (I’ll fetch up‑to‑date details).