# The 30 largest professional services firms in the Essonne department
Tamtam tracks 68 professional services firms headquartered in the Essonne department. This list ranks the 30 largest by number of employees on LinkedIn, led by UTAC, NOVELTY and KS SERVICES. Their median headcount is 113. Half of them were founded in 1994 or later. The most common headquarters are Les Ulis (8), Massy (6) and Orsay (2).
These are professional services firms in Essonne, predominantly mid-sized companies with a strong presence in IT services and engineering. UTAC, with 1249 employees, specializes in advancing the mobility industry towards a safer and cleaner future. NOVELTY provides technical support for events, while KS SERVICES offers tailored logistics and general services. APIXIT focuses on cybersecurity, infrastructure, and cloud solutions.
The companies are concentrated in towns like Les Ulis, Orsay, and Massy. Several firms, such as NBTECH and ADVANCE Engineering, specialize in engineering services for sectors like automotive, aerospace, and nuclear. There is also a notable cluster of IT services and consulting companies, including DSI GROUP, IJNEXT, and INTERDATA.
馃嚝馃嚪 Essonne 路 30 companies 路 Updated Nov 11, 2026
| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [UTAC](https://www.tamtam.ai/c/utac) (utac.com)
Advancing mobility industry towards safer, cleaner future. Provides large range of services to bring vehicles to market. | Motor Vehicle Manufacturing | 馃嚝馃嚪 Linas | 1,249 | |
| 2 | [NOVELTY](https://www.tamtam.ai/c/novelty) (novelty.fr)
Specialist in technical support for event industries, offering services like audiovisual equipment rental, engineering, sales, installation, and maintenance of audiovisual systems | Events Services | 馃嚝馃嚪 Longjumeau | 835 | 1973 |
| 3 | [KS SERVICES](https://www.tamtam.ai/c/ks-services) (ks-services.com)
Provides tailored logistics, general services, security, and administrative support through on-site teams committed to operational excellence and continuous process improvement results. | Transportation, Logistics, Supply Chain and Storage | 馃嚝馃嚪 Orsay | 501 | 1991 |
| 4 | [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 |
| 5 | [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 |
| 6 | [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 |
| 7 | [COMEARTH](https://www.tamtam.ai/c/comearth) (comearth-france.com)
An agile and custom B2B and B2C customer relationship outsourcing center in France, dedicated to delivering quality services for a memorable customer experience | Business Consulting and Services | 馃嚝馃嚪 Orsay | 214 | 2004 |
| 8 | [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 |
| 9 | [IJNEXT](https://www.tamtam.ai/c/ijnext) (ijnext.com)
A major player in IT infrastructure services and innovative technologies, offering comprehensive solutions in security, performance, and automation through three interconnected companies | IT Services and IT Consulting | 馃嚝馃嚪 Les Ulis | 202 | |
| 10 | [INTERDATA](https://www.tamtam.ai/c/interdata) (interdata.fr)
French company providing certified expertise in IT networks, SI security, and observability for over 40 years Offering tailored services for reliable, scalable, and secure network management | Computer Networking Products | 馃嚝馃嚪 Les Ulis | 188 | 1979 |
| 11 | [ORANO DS- DEMANTELEMENT ET SERVICES](https://www.tamtam.ai/c/orano-ds-demantelement-et-services)
A utilities company in France specializing in dismantling and services related to nuclear energy and waste management | Utilities | 馃嚝馃嚪 Gif-sur-Yvette | 177 | |
| 12 | [AVL in France](https://www.tamtam.ai/c/avl-in-france) (avl.com)
Develops, simulates, and tests engines, transmissions, powertrains, and batteries. Provides turnkey test and simulation solutions, software, instrumentation, and services for the mobility industry. | Motor Vehicle Manufacturing | 馃嚝馃嚪 Palaiseau | 162 | 1990 |
| 13 | [Stem Groupe](https://www.tamtam.ai/c/stem-groupe) (stemgroupe.fr)
Specializing in providing cleaning and facility management services to businesses and public institutions, including maintenance, security, landscaping, and pest control | Environmental Services | 馃嚝馃嚪 Verrieres Le Buisson | 144 | 1956 |
| 14 | [Exatech](https://www.tamtam.ai/c/exatech) (global.exatech-group.com)
Collaboration with universities and agencies to optimize and secure paper-based and digital examinations and assessments through innovative technology solutions. | Software Development | 馃嚝馃嚪 Verri猫res-le-Buisson | 114 | 1994 |
| 15 | [KYOCERA Document Solutions France](https://www.tamtam.ai/c/kyocera-document-solutions-france) (kyoceradocumentsolutions.fr)
Provide comprehensive document management solutions including software, hardware, and professional services to support digital transformation and reduce environmental impact. | IT Services and IT Consulting | 馃嚝馃嚪 Massy | 113 | 1959 |
| 16 | [EBS Group France](https://www.tamtam.ai/c/ebs-group-france) (ebsgroup.fr)
Provides comprehensive IT services and equipment management, offering tailored software and hardware solutions to small and medium businesses. | Software Development | 馃嚝馃嚪 Bi猫vres | 88 | |
| 17 | [SOLUTYS Group](https://www.tamtam.ai/c/solutys-group) (solutys.com)
Specializes in automatic identification, network and cybersecurity solutions, offering comprehensive products and services to large companies and SMEs. | IT Services and IT Consulting | 馃嚝馃嚪 Lisses | 65 | 2002 |
| 18 | [NUCLETUDES](https://www.tamtam.ai/c/nucletudes) (nucletudes.ariane.group)
Specialized in engineering and testing for protection against severe radiative and electromagnetic aggressions, as a subsidiary of a global aerospace company | Aviation and Aerospace Component Manufacturing | 馃嚝馃嚪 Les Ulis | 61 | 1966 |
| 19 | [IPSILAN NETWORKS](https://www.tamtam.ai/c/ipsilan-networks) (ipsilan-networks.fr)
Integration of network and telecom solutions with strong technical expertise, client partnership, and proactive business development for tailored support. | IT Services and IT Consulting | 馃嚝馃嚪 Bi猫vres | 58 | 1997 |
| 20 | [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 |
| 21 | [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 |
| 22 | [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 |
| 23 | [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 |
| 24 | [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 |
| 25 | [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 |
| 26 | [DML](https://www.tamtam.ai/c/dml) (dml.fr)
An ICT services provider established in 1998, offering technical expertise, consulting, project management, and technology integration in Security, CyberSecurity, Identity Management, and Messaging | IT Services and IT Consulting | 馃嚝馃嚪 Les Ulis | 34 | 1978 |
| 27 | [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 |
| 28 | [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 |
| 29 | [Ad Consulting](https://www.tamtam.ai/c/ad-consulting) (ad-consulting.paris)
An independent consulting firm specializing in finance, professional and real estate loans, and wealth management for professionals and self-employed professionals | Insurance | 馃嚝馃嚪 La Norville | 27 | |
| 30 | [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 |
## 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)
- [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)
- [Consulting firms in the Essonne department](https://www.tamtam.ai/l/consulting-firms-essonne) (40)
- [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
- [Professional services firms in France](https://www.tamtam.ai/l/professional-services-firms-france) (6,611)
- [Professional services firms in 脦le-de-France](https://www.tamtam.ai/l/professional-services-firms-ile-de-france) (3,377)
- [Professional services firms in Auvergne-Rh么ne-Alpes](https://www.tamtam.ai/l/professional-services-firms-auvergne-rhone-alpes) (711)
- [Professional services firms in the Hauts-de-Seine department](https://www.tamtam.ai/l/professional-services-firms-hauts-de-seine) (629)
- [Professional services firms in Provence-Alpes-C么te d'Azur](https://www.tamtam.ai/l/professional-services-firms-provence-alpes-cote-dazur) (433)
- [Professional services firms in the Rh么ne department](https://www.tamtam.ai/l/professional-services-firms-rhone) (400)
- [Professional services firms in Occitanie](https://www.tamtam.ai/l/professional-services-firms-occitanie) (399)
- [Professional services firms in Grand Est](https://www.tamtam.ai/l/professional-services-firms-grand-est) (316)
- [Professional services firms in Nouvelle-Aquitaine](https://www.tamtam.ai/l/professional-services-firms-nouvelle-aquitaine) (308)
- [Professional services firms in Hauts-de-France](https://www.tamtam.ai/l/professional-services-firms-hauts-de-france) (260)
- [Professional services firms in Pays de la Loire](https://www.tamtam.ai/l/professional-services-firms-pays-de-la-loire) (254)
- [Professional services firms in the Bouches-du-Rh么ne department](https://www.tamtam.ai/l/professional-services-firms-bouches-du-rhone) (249)
- [Professional services firms in the Haute-Garonne department](https://www.tamtam.ai/l/professional-services-firms-haute-garonne) (208)
- [Professional services firms in the Nord department](https://www.tamtam.ai/l/professional-services-firms-nord) (178)
- [Professional services firms in Brittany](https://www.tamtam.ai/l/professional-services-firms-brittany) (167)
- [Professional services firms in the Loire-Atlantique department](https://www.tamtam.ai/l/professional-services-firms-loire-atlantique) (158)
- [Professional services firms in the Gironde department](https://www.tamtam.ai/l/professional-services-firms-gironde) (151)
- [Professional services firms in Normandy](https://www.tamtam.ai/l/professional-services-firms-normandy) (114)
- [Professional services firms in the Yvelines department](https://www.tamtam.ai/l/professional-services-firms-yvelines) (108)
- [Professional services firms in Paris](https://www.tamtam.ai/l/professional-services-firms-paris) (2,241)
- [Professional services firms in Lyon](https://www.tamtam.ai/l/professional-services-firms-lyon) (265)
- [Professional services firms in Toulouse](https://www.tamtam.ai/l/professional-services-firms-toulouse) (139)
- [Professional services firms in Marseille](https://www.tamtam.ai/l/professional-services-firms-marseille) (123)
- [Professional services firms in Boulogne-Billancourt](https://www.tamtam.ai/l/professional-services-firms-boulogne-billancourt) (102)
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Source: https://www.tamtam.ai/l/professional-services-firms-essonne