Below are leading ESG consulting firms and firms that combine advisory with technology (data, measurement, reporting or carbon/accounting platforms). I grouped them so you can scan quickly — all are active in the U.S. and globally. I've cited recent industry/market sources for the most load-bearing items.

Major global consultancies with strong ESG advisory + tech capabilities

• McKinsey & Company — large sustainability & climate practice; advisory on net‑zero strategy, decarbonization, supply‑chain and climate risk. (mconsultingprep.com)
• Boston Consulting Group (BCG) — sustainability strategy, decarbonization, circular economy, and technology-enabled transformation. (mconsultingprep.com)
• Bain & Company — ESG/ESG strategy, decarbonization and private‑equity portfolio ESG work. (mconsultingprep.com)
• Accenture — broad sustainability and technology services (data platforms, green IT, digital for sustainability). (mconsultingprep.com)
• Deloitte, PwC, EY, KPMG (the “Big Four”) — full-service ESG practices that combine advisory, assurance, regulatory reporting, and enterprise software integrations. (mconsultingprep.com)

Specialist sustainability / ESG consultancies

• ERM (Environmental Resources Management) — one of the largest specialist environmental/ESG consultancies; strong technical advisory and implementation experience. (mconsultingprep.com)
• South Pole, Anthesis, and similar specialist firms — climate and carbon services, offsets, and sustainability program delivery (often focused on operational emissions and value‑chain interventions). (mconsultingprep.com)

Boutique and fast-growing AI / tech-enabled consultancies

• Newer AI- and data-first boutiques and spinouts (ex‑consultant founders) are increasingly competing on faster, lower‑cost, technology-enabled ESG advisory. These firms often specialize in rapid data automation, modeling and analytics. (Market reporting on the trend). (businessinsider.com)

ESG technology / platform vendors commonly used alongside (or embedded in) consulting engagements

• Enablon (Wolters Kluwer) — enterprise EHS & ESG platform for data collection, reporting and disclosures; widely used in large enterprises. Recent awards and product updates highlight its enterprise SaaS capabilities. (wolterskluwer.com)
• Persefoni — carbon accounting & management platform (finance‑grade carbon accounting). Persefoni and similar carbon platforms are frequently recommended for GHG inventory and scenario planning. (persefoni.com)
• Other commonly cited platforms (examples you’ll encounter in vendor shortlists): Measurabl, FigBytes, Sphera, Workiva, Diligent/OneTrust integrations, and major data providers (MSCI, S&P Global / Trucost, Sustainalytics) — many consultancies partner or integrate with one or more of these platforms for data, scoring and disclosure workflows. (See platform comparison roundups used by consultancies and sustainability teams). (persefoni.com)

How buyers typically select a firm or platform

• For strategy and board-level advisement: top-tier strategy firms (McKinsey/BCG/Bain) or Big Four — they provide C‑suite strategy, regulatory support, and often partner with tech vendors. (mconsultingprep.com)
• For technical emissions accounting, measurement and implementation: specialist consultancies (ERM, Anthesis, South Pole) or consultancies that embed carbon/accounting platforms. (mconsultingprep.com)
• For enterprise reporting, disclosure automation and audit readiness: Big Four + enterprise ESG SaaS (Enablon, Workiva, Sphera, etc.). (wolterskluwer.com)

If you want a short, tailored recommendation I can provide:

• A 3–firm shortlist matched to your company size (SMB / mid‑market / large enterprise) and highest priorities (carbon accounting, regulatory reporting, supply‑chain risk, investor disclosures).
• Or a vendor short-list (3–5 platforms) focused on GHG accounting, integrated reporting, or software that’s easiest to implement with your ERP/finance systems.

Which would you prefer?