# List of consulting firms in the Loire-Atlantique department

Tamtam tracks 94 consulting firms headquartered in the Loire-Atlantique department. This list ranks the 30 largest by number of employees on LinkedIn, led by Catamania, Sce Aménagement & Environnement and Groupe Sigma. Their median headcount is 182. Half of them were founded in 2001 or later. The most common headquarters are Nantes (13), Saint-Herblain (10) and La Chapelle-sur-Erdre (3).

The Loire-Atlantique department hosts numerous consulting firms, predominantly in IT services and engineering, with a mix of established companies and younger firms. Catamania, founded in 1999, provides digital transformation services for banking and retail. Groupe Sigma, established in 1972, focuses on enhancing performance through digital impact. Sce Aménagement & Environnement, from 1982, offers sustainable development services, while Conserto, founded in 2013, specializes in IT consulting across cloud and digital domains. TECHNA, an independent international group founded in 1964, specializes in precision nutrition and breeding techniques for agricultural production.

Many of these companies, such as Catamania, ASI ®, Conserto, and AIS, are headquartered in Saint-Herblain, indicating a concentration of IT and consulting expertise in this specific area within Loire-Atlantique. The presence of firms like SOFRESID ENGINEERING and Atlantic Ingénierie alongside IT consultants suggests a diverse yet interconnected consulting landscape.

🇫🇷 Loire-Atlantique · 30 companies · Updated Nov 15, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Catamania](https://www.tamtam.ai/c/catamania) (catamania.com)<br>Provides digital transformation services, consulting, software publishing, and information system architecture for banking, insurance, and retail sectors across international agencies using diverse technical expertise. | IT Services and IT Consulting | 🇫🇷 Saint-Herblain | 797 | 1999 |
| 2 | [Sce Aménagement & Environnement](https://www.tamtam.ai/c/sce-amenagement-and-environnement) (sce.fr)<br>Sustainable development firm offering urban planning, civil engineering, and environmental services globally with 45+ years of experience and 500 professionals | Environmental Services | 🇫🇷 Nantes | 625 | 1982 |
| 3 | [Groupe Sigma](https://www.tamtam.ai/c/groupe-sigma-la-chapelle-sur-erdre) (sigma.fr)<br>The company aims to enhance performance through digital impact, innovate eco-friendly solutions, and build digital ecosystems with expert dialogue | IT Services and IT Consulting | 🇫🇷 La Chapelle-sur-Erdre | 607 | 1972 |
| 4 | [ASI ®](https://www.tamtam.ai/c/asi) (asi.fr)<br>Working towards a responsible digital world dedicated to serving humanity | IT Services and IT Consulting | 🇫🇷 Saint-Herblain | 590 | 1993 |
| 5 | [Conserto](https://www.tamtam.ai/c/conserto) (conserto.pro)<br>Offers IT consulting and expertise services across cloud, digital, and embedded domains through consulting, delivery centers, and labs models. | IT Services and IT Consulting | 🇫🇷 Saint-Herblain | 555 | 2013 |
| 6 | [4CAD Group](https://www.tamtam.ai/c/4cad-group) (4cadgroup.com)<br>The company offers PLM, ERP, and IoT tools to help organizations optimize their information systems for increased industrial efficiency | Software Development | 🇫🇷 Bouguenais | 463 | 2004 |
| 7 | [Atlantic Ingénierie](https://www.tamtam.ai/c/atlantic-ingenierie) (atlantic-ingenierie.com)<br>Engineering firm specializing in energy and telecommunication network deployment, providing expert studies and support for projects of all sizes. | Business Consulting and Services | 🇫🇷 Saint-Herblain | 385 | 2001 |
| 8 | [TECHNA](https://www.tamtam.ai/c/techna) (groupe-techna.com)<br>Independent international group, expert in precision nutrition, breeding techniques, and natural health, serving agricultural production for 60 years. | Farming | 🇫🇷 Couëron | 343 | 1964 |
| 9 | [AIS](https://www.tamtam.ai/c/ais) (groupeais.fr)<br>AIS is a human-centric company providing expertise to clients since 1985, focusing on professional growth and fulfillment of its employees | IT Services and IT Consulting | 🇫🇷 Saint-Herblain | 289 | 1985 |
| 10 | [SOFRESID ENGINEERING](https://www.tamtam.ai/c/sofresid-engineering) (sofresid-engineering.com)<br>Global engineering company with high value-added services in oil, gas, shipbuilding, steel, and construction industries. Offers turnkey projects, studies, procurement, and supervision. | Engineering Services | 🇫🇷 Saint-Herblain | 230 | 1958 |
| 11 | [Younup](https://www.tamtam.ai/c/younup) (younup.fr)<br>This company offers IT services, supporting clients throughout the software lifecycle from requirements to production, focusing on web, DevOps, data, AI, agility, mobile, and cloud. | IT Services and IT Consulting | 🇫🇷 Nantes | 224 | 2019 |
| 12 | [COCERTO](https://www.tamtam.ai/c/cocerto) (cocerto.fr)<br>Provides comprehensive accounting, audit, payroll, legal support, and digital tools to optimize and secure business operations with personalized service. | Accounting | 🇫🇷 Nantes | 200 | 1971 |
| 13 | [MECA](https://www.tamtam.ai/c/meca-nantes) (cluster-meca.fr)<br>A cluster of companies offering mechanical analysis expertise to ensure safety and feasibility of constructions through material behavior, design, and stress calculation | Business Consulting and Services | 🇫🇷 Nantes | 194 | 2006 |
| 14 | [GROUPE SYD](https://www.tamtam.ai/c/groupe-syd) (syd.fr)<br>Specializing in digital transformation, the company offers consultancy, project management, infrastructure services, Microsoft solutions integration, application development, and Microsoft expertise, emphasizing customer satisfaction and trust | IT Services and IT Consulting | 🇫🇷 Saint-Herblain | 190 | 1999 |
| 15 | [Compas](https://www.tamtam.ai/c/compas) (lecompas.fr)<br>Specializing in social observation of territories, creating observatories, conducting studies, and providing training for local governments to address social realities effectively | Research Services | 🇫🇷 Nantes | 182 | 1996 |
| 16 | [Cerfrance Loire-Atlantique](https://www.tamtam.ai/c/cerfrance-loire-atlantique) (loire-atlantique.cerfrance.fr)<br>Provide accounting, strategic, fiscal, legal, social, HR, and IT consulting to support local entrepreneurs and business leaders' overall performance. | Business Consulting and Services | 🇫🇷 La Chapelle-sur-Erdre | 177 | 1958 |
| 17 | [EVEA](https://www.tamtam.ai/c/evea) (evea-conseil.com)<br>Assists organizations in enhancing environmental and social performance of products, services, and activities through consulting, software tools, and training. | Business Consulting and Services | 🇫🇷 Nantes | 167 | 2005 |
| 18 | [ORINOX](https://www.tamtam.ai/c/orinox) (orinox.com)<br>Software consulting and plant design firm specializing in digitalization using AVEVA software suite for engineering, asset data visualization, resources management, simulation, and training | Business Consulting and Services | 🇫🇷 Chateaubriant | 166 | 2008 |
| 19 | [MOCA](https://www.tamtam.ai/c/moca) (asi.fr)<br>MOCA by ASI specializes in offering technical expertise and support for Microsoft solutions to users within the Microsoft ecosystem | IT Services and IT Consulting | 🇫🇷 Saint-Herblain | 159 | 2022 |
| 20 | [Valeuriad](https://www.tamtam.ai/c/valeuriad) (valeuriad.fr)<br>Experts in transforming complex information systems, providing technical excellence in AI, data engineering, cloud, and infrastructure for large organizations. | IT Services and IT Consulting | 🇫🇷 Nantes | 156 | 2015 |
| 21 | [Capaciti](https://www.tamtam.ai/c/capaciti) (capaciti.com)<br>A regional leader in cybersecurity, providing specialized services in consulting, engineering, and system infrastructure support with offices in France and international project capabilities | IT Services and IT Consulting | 🇫🇷 Carquefou | 150 | 1999 |
| 22 | [KOSMOS](https://www.tamtam.ai/c/kosmos-nantes) (kosmos-education.com)<br>Specializing in digital education solutions, this company implements web portals, e-portfolios, mobile apps, and other digital tools for schools | IT Services and IT Consulting | 🇫🇷 Nantes | 141 | 1998 |
| 23 | [kanoma](https://www.tamtam.ai/c/kanoma) (kanoma.fr)<br>Experts guide clients digital transformation, from design to production, focusing on agile projects, development, product design, and organizational change. | IT Services and IT Consulting | 🇫🇷 Nantes | 128 | 2018 |
| 24 | [EXEIS Conseil](https://www.tamtam.ai/c/exeis-conseil) (exeisconseil.com)<br>Operational consulting firm supporting organizations in mastering transformations, addressing organizational, performance, and digitization challenges across multiple industries. | Business Consulting and Services | 🇫🇷 Nantes | 104 | 2009 |
| 25 | [Collectif Energie](https://www.tamtam.ai/c/collectif-energie) (collectifenergie.com)<br>An energy collective for small and medium-sized businesses in France, providing access to discounted electricity and gas through strategic procurement solutions | Business Consulting and Services | 🇫🇷 Nantes | 104 | 2015 |
| 26 | [A5sys](https://www.tamtam.ai/c/a5sys) (a5sys.com)<br>Founded in 2001, the company specializes in IT services focusing on business intelligence, databases, and application development | IT Services and IT Consulting | 🇫🇷 Saint-Herblain | 92 | 2001 |
| 27 | [Le Phare](https://www.tamtam.ai/c/le-phare) (lephare.com)<br>Digital product factory for SMEs, ETIs, and industries Provides digital transformation consulting and custom platforms to accelerate B2B and B2B2C businesses | Technology, Information and Internet | 🇫🇷 Nantes | 87 | 2000 |
| 28 | [Mercuria](https://www.tamtam.ai/c/mercuria) (mercuria.fr)<br>Advises and supports businesses with SaaS, Cloud, or hosted solutions for accounting, financial, payroll, and HR management software, working with reliable publishers. | Software Development | 🇫🇷 La Chapelle-sur-Erdre | 82 | 1999 |
| 29 | [IDEUZO](https://www.tamtam.ai/c/ideuzo) (ideuzo.com)<br>IDEUZO is a specialized agency in HR consulting and communication, guiding organizations to enhance their recruitment strategies through sourcing, branding, and influence | Advertising Services | 🇫🇷 Nantes | 81 | 2007 |
| 30 | [ATYX](https://www.tamtam.ai/c/atyx) (atyx.fr)<br>Provider of high-quality technical solutions for global projects in energy, process industry, infrastructure, and urban development sectors Specializing in conventional and renewable energy | Engineering Services | 🇫🇷 Saint-Herblain | 80 | 2001 |

## How this list is built

Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 15, 2026.

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## The same list elsewhere in France

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Source: https://www.tamtam.ai/l/consulting-firms-loire-atlantique