The companies in Essonne are primarily large, well-established firms with significant R&D capabilities, reflecting a strong industrial and technological base. They span diverse sectors including manufacturing, healthcare, and advanced technology.
Key players include Réseau DEF, specializing in fire safety systems, LFB, a pharmaceutical manufacturer, ONERA - The French Aerospace Lab, focused on aerospace and defense research, and ASN, which designs and maintains submarine cable systems. A notable pattern is the concentration of headquarters in cities like Palaiseau and Les Ulis, indicating a regional hub for technological and industrial development.
| # | Company | Employees | |||
|---|---|---|---|---|---|
| 1 |
Réseau DEFreseau-def.com
International network of expert companies providing detection, extinguishing, smoke extraction, and exit management systems through manufacturing and research facilities across several countries. |
3,484 | |||
| 2 |
LFBgroupe-lfb.com
Develops, manufactures, and markets medicinal products for serious, often rare diseases in Hemostasis, Immunology, and Intensive Care, with a focus on plasma-derived products and biotechnologies. |
2,733 | |||
| 3 |
HORIBA Francehoriba.com
HORIBA France manufactures instruments to help individuals tackle all their challenges |
2,200 | |||
| 4 |
ONERA - The French Aerospace Labonera.fr
Researching future aerospace and defense challenges, contributing to industry competitiveness through expertise in all related disciplines and technologies. |
2,097 | |||
| 5 | 1,717 | ||||
| 6 |
Menardmenard-group.com
A global leader in ground improvement works using innovative technologies to optimize geotechnical conditions for various infrastructure projects worldwide |
1,590 | |||
| 7 |
TechnicAtometechnicatome.com
Specialized in compact nuclear reactor design, construction, and maintenance for various sectors including naval propulsion, research, medicine, and energy |
1,467 | |||
| 8 | 1,249 | ||||
| 9 |
CENTRE HOSPITALIER SUD FRANCILIENchsf.fr
Public healthcare institution serving one million people in southern Île-de-France, providing medical services and hospital care to the community. |
1,219 | |||
| 10 |
Eurostyle Systemseurostyle-systems.fr
Design and production of industrial solutions specializing in high-precision plastics processing and leather materials for global automotive markets across fourteen production sites. |
1,158 | |||
| 11 |
HORIBA for Materialshoriba.com
Researching, developing new materials, improving manufacturing, and implementing recycling solutions for sustainability across the material supply chain. |
1,053 | |||
| 12 | 1,018 | ||||
| 13 |
Télécom Paristelecom-paris.fr
A leading educational institution in ICT, offering various programs in engineering, masters, and PhD, with a focus on innovation and entrepreneurship in the digital world |
953 | |||
| 14 |
Infovistainfovista.com
Empowers service providers and enterprises with data-driven solutions for optimizing network performance, enhancing customer experience, and driving business success. |
834 | |||
| 15 |
L-Acousticsl-acoustics.com
Leading manufacturer of professional sound solutions founded in 1984 near Paris, with presence in over 80 countries and specializing in modern line array technology and multichannel sound systems |
700 | |||
Want more companies than this list?This page shows the largest ones only. Connect to Tamtam to see every company that matches, filter by size, industry or growth, and reach their decision-makers. | |||||
| 16 |
Horoquartzhoroquartz.com
Provides integrated solutions for workforce management, planning optimization, activity tracking, access control, and identity management, serving over 5000 clients globally. |
568 | |||
| 17 |
Vernet Groupvernet-group.com
Family company, world leader in thermal regulation, designing and manufacturing thermostats and thermostatic elements for automotive, heating, and plumbing industries. |
418 | |||
| 18 |
Synchrotron SOLEILsynchrotron-soleil.fr
Third generation synchrotron providing advanced experimental facilities for material geometry and properties research, serving diverse scientific users worldwide. |
403 | |||
| 19 |
Pasqalpasqal.com
The company specializes in building programmable quantum simulators and computers using neutral atoms in optical tweezers for quantum information processing |
297 | |||
| 20 | 242 | ||||
| 21 |
Eurostyle Systemseurostyle-systems.fr
A branch of the GMD Group specializing in manufacturing automotive plastic components for OEMs and Tier 1 suppliers with 2500 employees and a turnover of 300 M€ in 2018 |
234 | |||
| 22 |
Exotrailexotrail.com
Develops and operates propulsion systems, mission simulation software, and orbital transfer vehicles for efficient, sustainable space mobility, enabling telecommunication, Earth observation, space exploration. |
215 | |||
| 23 |
PMC Isochempmcisochem.fr
Custom manufacturing of APIs, intermediates, and excipients with drug delivery solutions including Vitamin E TPGS and amino acid polymers for pharmaceuticals. |
215 | |||
| 24 |
PCASseqens.com
Develops and produces complex molecules using advanced technologies for global leaders in Life Sciences and Innovative Technologies. Part of a larger international group. |
213 | |||
| 25 |
UMS - United Monolithic Semiconductorsums-rf.com
Designs and manufactures GaAs and GaN based RF and millimeter-wave integrated circuits and provides advanced foundry services for critical applications. |
210 | |||
| 26 |
Anton Paar Franceanton-paar.com
Sales of measurement and laboratory instruments for density, concentration, rheometry, and CO2 analysis serving industry and research sectors. |
201 | |||
| 27 |
SOPHYSAsophysa.com
Develops neurosurgical implants, including adjustable valves for hydrocephalus and intracranial pressure monitoring systems, offering advanced solutions for neurological conditions. |
195 | |||
| 28 |
Eurobio Scientific FReurobio-scientific.com
Develops, manufactures, and commercializes in-vitro diagnostic products for hospitals and private medical biology laboratories, specializing in transplantation, infectious diseases, and life sciences. |
193 | |||
| 29 |
ADALTRAadaltra.fr
Specializing in communication systems for various environments such as offices, hotels, hospitals, airports, stadiums, and more, our solutions are designed by CAE GROUPE |
182 | |||
| 30 |
Sefi-Intraforfayat.com
Specialized in deep foundations and underground works, this company offers extensive expertise in various techniques, from pilings to injections, with a large equipment fleet since 1965 |
181 | |||
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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 1,149
- Multinational companies in the Essonne department 156
- Manufacturers in the Essonne department 127
- Hardware manufacturers in the Essonne department 114
- Distributors and wholesalers in the Essonne department 76
- IT Services and IT Consulting companies in the Essonne department 70
- Professional services firms in the Essonne department 68
- Public sector organisations in the Essonne department 66
- Aerospace and defence companies in the Essonne department 65
- IT services companies in the Essonne department 60
- Retail chains in the Essonne department 59
- Construction companies in the Essonne department 56
- Software Development companies in the Essonne department 51
- Pharmaceutical companies in the Essonne department 45
- Electronics and semiconductor companies in the Essonne department 44
- Research institutes in the Essonne department 42
- Events Services companies in the Essonne department 41
- SaaS companies in the Essonne department 41
- Consulting firms in the Essonne department 40
- Family-owned companies in the Essonne department 38
- Contract manufacturers in the Essonne department 35
- Research Services companies in the Essonne department 35
- Critical infrastructure operators in the Essonne department 32
- Education providers in the Essonne department 30
The same list elsewhere in France
- Companies with in-house R&D in France 8,750
- Companies with in-house R&D in Île-de-France 2,695
- Companies with in-house R&D in Auvergne-Rhône-Alpes 1,460
- Companies with in-house R&D in Occitanie 680
- Companies with in-house R&D in Grand Est 640
- Companies with in-house R&D in Provence-Alpes-Côte d'Azur 613
- Companies with in-house R&D in Nouvelle-Aquitaine 566
- Companies with in-house R&D in the Hauts-de-Seine department 510
- Companies with in-house R&D in the Rhône department 509
- Companies with in-house R&D in Pays de la Loire 480
- Companies with in-house R&D in Hauts-de-France 410
- Companies with in-house R&D in Brittany 366
- Companies with in-house R&D in the Haute-Garonne department 323
- Companies with in-house R&D in the Bouches-du-Rhône department 321
- Companies with in-house R&D in the Isère department 304
- Companies with in-house R&D in Bourgogne-Franche-Comté 261
- Companies with in-house R&D in the Nord department 237
- Companies with in-house R&D in Normandy 227
- Companies with in-house R&D in the Gironde department 225
- Companies with in-house R&D in the Loire-Atlantique department 207
- Companies with in-house R&D in Centre-Val de Loire 195
- Companies with in-house R&D in Paris 1,249
- Companies with in-house R&D in Lyon 192
- Companies with in-house R&D in Toulouse 172