# Top 30 consulting firms in the Essonne department
Tamtam tracks 40 consulting firms headquartered in the Essonne department. This list ranks the 30 largest by number of employees on LinkedIn, led by APIXIT, G4 and NBTECH. Their median headcount is 36. Half of them were founded in 2007 or later. The most common headquarters are Massy (7), Les Ulis (5) and Gif-sur-Yvette (2).
The consulting firms in Essonne are predominantly mid-sized companies specialized in engineering and IT services. APIXIT provides cybersecurity, infrastructure, and cloud solutions. NBTECH offers technical studies and industrial engineering for various sectors. ADVANCE Engineering focuses on complex nuclear projects, and DSI GROUP is an engineering services company emphasizing staff development.
Most of these firms, such as G4 in information management, Cyrias in cloud solution integration, and EZYTAIL in supply chain management, were founded between 2006 and 2018. A notable concentration of headquarters is observed in Les Ulis and Massy, indicating these areas as key hubs for consulting activities within the department.
馃嚝馃嚪 Essonne 路 30 companies 路 Updated Nov 11, 2026
| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [APIXIT](https://www.tamtam.ai/c/apixit) (apixit.fr)
Provides cybersecurity, infrastructure, and cloud solutions, supporting clients through audits, consulting, integration, maintenance, and managed services for digital transformation. | IT Services and IT Consulting | 馃嚝馃嚪 Les Ulis | 303 | 1992 |
| 2 | [G4](https://www.tamtam.ai/c/g4) (g4.fr)
G4 specializes in streamlining information management within companies, optimizing tools for strategic alignment and providing practical support and expertise | Information Services | 馃嚝馃嚪 Arpajon | 254 | 2006 |
| 3 | [NBTECH](https://www.tamtam.ai/c/nbtech) (nbtech.fr)
Technical studies, technology consulting, and industrial engineering services for automotive, aerospace, railway, and industrial maintenance sectors across France. | Engineering Services | 馃嚝馃嚪 Les Ulis | 244 | 2014 |
| 4 | [DSI GROUP](https://www.tamtam.ai/c/dsi-group) (group-dsi.com)
An engineering services company within the DSI GROUP, prioritizing staff development and customer relationships with a focus on flexibility and customer loyalty | IT Services and IT Consulting | 馃嚝馃嚪 Massy | 225 | 2007 |
| 5 | [ADVANCE Engineering](https://www.tamtam.ai/c/advance-engineering) (advance-eng.fr)
ADVANCE Engineering, a subsidiary of CERAP Pr茅vention, specializes in providing technical engineering services for complex projects in the nuclear sector | Engineering Services | 馃嚝馃嚪 Les Ulis | 205 | 2012 |
| 6 | [CERC (Cardiovascular European Research Center)](https://www.tamtam.ai/c/cerc-cardiovascular-european-research-center) (cerc-europe.org)
A leading European CRO founded by experienced physicians, specializing in clinical research, innovative techniques, and supporting young scientific leaders globally | Research Services | 馃嚝馃嚪 Massy | 84 | 2008 |
| 7 | [PROTECTIC](https://www.tamtam.ai/c/protectic) (protectic.fr)
Engineering company, intervening in large-scale industrial projects (aeronautics, space, defense, energy, transport). Accompanying major industrial players in product development. | IT Services and IT Consulting | 馃嚝馃嚪 Bi猫vres | 50 | 1983 |
| 8 | [DAF CONSEIL](https://www.tamtam.ai/c/daf-conseil) (dafconseil.com)
Specializes in automotive technical training, support, consulting, engineering, and web-based SaaS solutions for repair industry professionals. | Motor Vehicle Manufacturing | 馃嚝馃嚪 Lisses | 49 | 2006 |
| 9 | [SOL CONSEIL](https://www.tamtam.ai/c/sol-conseil) (vertical-sea.com)
Geotechnical consulting firm with over 35 years of experience offering services such as soil investigation, foundation design, and project management | Civil Engineering | 馃嚝馃嚪 Massy | 43 | 1982 |
| 10 | [Junior CentraleSup茅lec](https://www.tamtam.ai/c/junior-centralesupelec) (juniorcs.fr)
Junior CentraleSup茅lec is a student-run consulting firm offering services in digital, electronics, strategy, data analytics, and environment sectors with over 4500 future engineering graduates | IT Services and IT Consulting | 馃嚝馃嚪 Gif-sur-Yvette | 42 | 1969 |
| 11 | [Cyrias](https://www.tamtam.ai/c/cyrias) (cyrias.com)
Consulting and integration company specializes in assisting Purchasing and Finance Departments with implementing Cloud Solutions, offering expertise in digital transformation projects | Software Development | 馃嚝馃嚪 Massy | 42 | 2018 |
| 12 | [STYREL](https://www.tamtam.ai/c/styrel) (styrel.fr)
Engineering and training services specializing in industrial IT, embedded real-time computing, custom industrial PCs, test benches, and complete system integration. | Software Development | 馃嚝馃嚪 Le Plessis-P芒t茅 | 41 | 1984 |
| 13 | [EZYTAIL](https://www.tamtam.ai/c/ezytail) (ezytail.com)
Industrial supply chain management providing back office software, mutualized logistics, transportation solutions, ERP integration, and consulting for new and existing multi-channel retailing businesses. | Software Development | 馃嚝馃嚪 Grigny | 41 | 2010 |
| 14 | [SOCASS](https://www.tamtam.ai/c/socass) (socass.fr)
Specialized consulting company focusing on maintenance, operations, technology engineering, and innovation for industrial and tertiary sectors with a human-centered approach | Engineering Services | 馃嚝馃嚪 Les Ulis | 39 | 2007 |
| 15 | [CREATYM France](https://www.tamtam.ai/c/creatym-france) (creatym-france.com)
Specialized in engineering services, technical consulting, and studies for industrial actors, prioritizing human-centric approach, teamwork, and passion for technology to enhance client services | Industrial Machinery Manufacturing | 馃嚝馃嚪 Massy | 36 | 2013 |
| 16 | [CONSTRUIRE](https://www.tamtam.ai/c/construire) (construire-sa.fr)
The company provides engineering services for various industries, offering expertise in developing innovative solutions and technical support | Construction | 馃嚝馃嚪 Dourdan | 31 | 2019 |
| 17 | [IDETEC Environnement](https://www.tamtam.ai/c/idetec-environnement) (sites.google.com)
IDETEC Environment is a leading player in monitoring engineering, providing services from network diagnostics to site supervision, with a focus on quality and accreditation | Engineering Services | 馃嚝馃嚪 Villebon-sur-Yvette | 30 | 2000 |
| 18 | [Infass Syst猫mes](https://www.tamtam.ai/c/infass-systemes) (infass.com)
Development of tailored software solutions for insurance, temporary work, petroleum storage, and point-to-point transport industries with specialized expertise. | Software Development | 馃嚝馃嚪 Montgeron | 29 | 1973 |
| 19 | [Aryason Consulting](https://www.tamtam.ai/c/aryason-consulting) (aryason.fr)
Massy based firm specialized in providing professional advice on computer systems and software solutions with seven years of industry experience. | Software Development | 馃嚝馃嚪 Massy | 26 | 2013 |
| 20 | [CPP-SYSTEM](https://www.tamtam.ai/c/cpp-system)
A consulting and IT service company operating in Madagascar and France, specialized in digital payment, customer loyalty, and management solutions Coming soon! | IT Services and IT Consulting | 馃嚝馃嚪 Ballainvilliers | 24 | |
| 21 | [iNet System](https://www.tamtam.ai/c/inet-system) (inet-system.com)
A Paris-based company offers Apple technology advice, product resale, installation, integration, support contracts, and software development services | Software Development | 馃嚝馃嚪 Bi猫vres | 14 | 2004 |
| 22 | [IPC - Groupe Gengis](https://www.tamtam.ai/c/ipc-groupe-gengis) (ipc-gengis.fr)
A reliable partner providing tailored solutions in structural engineering since 1998, navigating complex regulations and economic challenges with a focus on client needs | Engineering Services | 馃嚝馃嚪 Palaiseau | 14 | 1998 |
| 23 | [Soler Conseil](https://www.tamtam.ai/c/soler-conseil) (solerconseil.fr)
A geotechnical engineering consulting firm with a laboratory, offering services from project initiation to completion, led by experienced professionals | Real Estate | 馃嚝馃嚪 Massy | 10 | 1986 |
| 24 | [Sol Paysage](https://www.tamtam.ai/c/sol-paysage) (solpaysage.fr)
Sol Paysage is an environmental consultancy specializing in landscape design, soil, and biodiversity They work on various scales from large territories to gardens, focusing on sustainable development | Environmental Services | 馃嚝馃嚪 Orsay | 10 | 1995 |
| 25 | [KAPSIKUM](https://www.tamtam.ai/c/kapsikum) (kapsikum.com)
KAPSIKUM supports the healthcare industries through its services and solutions | Business Consulting and Services | 馃嚝馃嚪 Saclay | 10 | 2022 |
| 26 | [INGCAD](https://www.tamtam.ai/c/ingcad) (ingcad.fr)
INGCAD is a specialized engineering consulting firm focusing on Civil Engineering drawing, with a dynamic team committed to meeting client needs | Civil Engineering | 馃嚝馃嚪 Saclay | 8 | 2016 |
| 27 | [A脣XOR](https://www.tamtam.ai/c/aexor) (aexor.eu)
AEXOR is an engineering firm specializing in ATEX industrial risk solutions, training, certification, chemical risk assessment, and pilot project development in various fields | Research Services | 馃嚝馃嚪 Les Ulis | 7 | 2007 |
| 28 | [Newasys](https://www.tamtam.ai/c/newasys) (newasys.com)
NEWASYS provides water consulting services to industries, communities, and private entities, focusing on reducing water consumption and promoting the reuse of non-conventional water sources | Water, Waste, Steam, and Air Conditioning Services | 馃嚝馃嚪 Gif-sur-Yvette | 7 | |
| 29 | [ATLANTIS GEOTECHNIQUE](https://www.tamtam.ai/c/atlantis-geotechnique) (atlantis-geotechnique.fr)
Expert geotechnical consulting office providing comprehensive soil studies, hydrogeological analysis, and pollution assessments for construction, infrastructure, and land development projects across France. | Construction | 馃嚝馃嚪 Ris-Orangis | 6 | 2024 |
| 30 | [ACTUAL PME, Conseil et Expertise Comptable](https://www.tamtam.ai/c/actual-pme-conseil-et-expertise-comptable) (actualpme.fr)
A consulting and accounting firm with two agencies in Essonne, offering financial, legal, tax, management, and social advisory services to businesses | Accounting | 馃嚝馃嚪 Linas | 6 | |
## 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 11, 2026.
## More company lists in the Essonne department
- [The largest companies in the Essonne department](https://www.tamtam.ai/l/largest-companies-essonne) (1,149)
- [Companies with in-house R&D in the Essonne department](https://www.tamtam.ai/l/r-and-d-companies-essonne) (198)
- [Multinational companies in the Essonne department](https://www.tamtam.ai/l/multinational-companies-essonne) (156)
- [Manufacturers in the Essonne department](https://www.tamtam.ai/l/manufacturers-essonne) (127)
- [Hardware manufacturers in the Essonne department](https://www.tamtam.ai/l/hardware-companies-essonne) (114)
- [Distributors and wholesalers in the Essonne department](https://www.tamtam.ai/l/distributors-and-wholesalers-essonne) (76)
- [IT Services and IT Consulting companies in the Essonne department](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-essonne) (70)
- [Professional services firms in the Essonne department](https://www.tamtam.ai/l/professional-services-firms-essonne) (68)
- [Public sector organisations in the Essonne department](https://www.tamtam.ai/l/public-sector-organisations-essonne) (66)
- [Aerospace and defence companies in the Essonne department](https://www.tamtam.ai/l/aerospace-and-defense-companies-essonne) (65)
- [IT services companies in the Essonne department](https://www.tamtam.ai/l/it-services-companies-essonne) (60)
- [Retail chains in the Essonne department](https://www.tamtam.ai/l/retail-chains-essonne) (59)
- [Construction companies in the Essonne department](https://www.tamtam.ai/l/construction-companies-essonne) (56)
- [Software Development companies in the Essonne department](https://www.tamtam.ai/l/software-development-companies-essonne) (51)
- [Pharmaceutical companies in the Essonne department](https://www.tamtam.ai/l/pharmaceutical-companies-essonne) (45)
- [Electronics and semiconductor companies in the Essonne department](https://www.tamtam.ai/l/electronics-companies-essonne) (44)
- [Research institutes in the Essonne department](https://www.tamtam.ai/l/research-institutes-essonne) (42)
- [Events Services companies in the Essonne department](https://www.tamtam.ai/l/events-services-companies-essonne) (41)
- [SaaS companies in the Essonne department](https://www.tamtam.ai/l/saas-companies-essonne) (41)
- [Family-owned companies in the Essonne department](https://www.tamtam.ai/l/family-owned-companies-essonne) (38)
- [Contract manufacturers in the Essonne department](https://www.tamtam.ai/l/contract-manufacturers-essonne) (35)
- [Research Services companies in the Essonne department](https://www.tamtam.ai/l/research-services-companies-essonne) (35)
- [Critical infrastructure operators in the Essonne department](https://www.tamtam.ai/l/critical-infrastructure-operators-essonne) (32)
- [Education providers in the Essonne department](https://www.tamtam.ai/l/education-companies-essonne) (30)
## The same list elsewhere in France
- [Consulting firms in France](https://www.tamtam.ai/l/consulting-firms-france) (4,252)
- [Consulting firms in 脦le-de-France](https://www.tamtam.ai/l/consulting-firms-ile-de-france) (2,408)
- [Consulting firms in the Hauts-de-Seine department](https://www.tamtam.ai/l/consulting-firms-hauts-de-seine) (563)
- [Consulting firms in Auvergne-Rh么ne-Alpes](https://www.tamtam.ai/l/consulting-firms-auvergne-rhone-alpes) (412)
- [Consulting firms in the Rh么ne department](https://www.tamtam.ai/l/consulting-firms-rhone) (242)
- [Consulting firms in Occitanie](https://www.tamtam.ai/l/consulting-firms-occitanie) (236)
- [Consulting firms in Provence-Alpes-C么te d'Azur](https://www.tamtam.ai/l/consulting-firms-provence-alpes-cote-dazur) (233)
- [Consulting firms in Nouvelle-Aquitaine](https://www.tamtam.ai/l/consulting-firms-nouvelle-aquitaine) (166)
- [Consulting firms in Grand Est](https://www.tamtam.ai/l/consulting-firms-grand-est) (165)
- [Consulting firms in Hauts-de-France](https://www.tamtam.ai/l/consulting-firms-hauts-de-france) (161)
- [Consulting firms in Pays de la Loire](https://www.tamtam.ai/l/consulting-firms-pays-de-la-loire) (161)
- [Consulting firms in the Haute-Garonne department](https://www.tamtam.ai/l/consulting-firms-haute-garonne) (145)
- [Consulting firms in the Bouches-du-Rh么ne department](https://www.tamtam.ai/l/consulting-firms-bouches-du-rhone) (129)
- [Consulting firms in the Nord department](https://www.tamtam.ai/l/consulting-firms-nord) (115)
- [Consulting firms in Brittany](https://www.tamtam.ai/l/consulting-firms-brittany) (99)
- [Consulting firms in the Loire-Atlantique department](https://www.tamtam.ai/l/consulting-firms-loire-atlantique) (94)
- [Consulting firms in the Gironde department](https://www.tamtam.ai/l/consulting-firms-gironde) (82)
- [Consulting firms in the Yvelines department](https://www.tamtam.ai/l/consulting-firms-yvelines) (72)
- [Consulting firms in Paris](https://www.tamtam.ai/l/consulting-firms-paris) (1,532)
- [Consulting firms in Lyon](https://www.tamtam.ai/l/consulting-firms-lyon) (163)
- [Consulting firms in Toulouse](https://www.tamtam.ai/l/consulting-firms-toulouse) (98)
- [Consulting firms in Boulogne-Billancourt](https://www.tamtam.ai/l/consulting-firms-boulogne-billancourt) (88)
- [Consulting firms in Levallois-Perret](https://www.tamtam.ai/l/consulting-firms-levallois-perret) (83)
- [Consulting firms in Neuilly-sur-Seine](https://www.tamtam.ai/l/consulting-firms-neuilly-sur-seine) (73)
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Source: https://www.tamtam.ai/l/consulting-firms-essonne