# Top 30 companies with in-house R&D in the Essonne department

Tamtam tracks 198 companies with in-house R&D headquartered in the Essonne department. This list ranks the 30 largest by number of employees on LinkedIn, led by Réseau DEF, LFB and HORIBA France. Their median headcount is 700. Half of them were founded in 1976 or later. The most common headquarters are Les Ulis (6), Massy (6) and Palaiseau (5).

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.

🇫🇷 Essonne · 30 companies · Updated Nov 11, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Réseau DEF](https://www.tamtam.ai/c/reseau-def) (reseau-def.com)<br>International network of expert companies providing detection, extinguishing, smoke extraction, and exit management systems through manufacturing and research facilities across several countries. | Appliances, Electrical, and Electronics Manufacturing | 🇫🇷 Massy | 3,484 | 1958 |
| 2 | [LFB](https://www.tamtam.ai/c/lfb) (groupe-lfb.com)<br>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. | Pharmaceutical Manufacturing | 🇫🇷 Les Ulis | 2,733 | 1994 |
| 3 | [HORIBA France](https://www.tamtam.ai/c/horiba-france) (horiba.com)<br>HORIBA France manufactures instruments to help individuals tackle all their challenges | Measuring and Control Instrument Manufacturing | 🇫🇷 Palaiseau | 2,200 |  |
| 4 | [ONERA - The French Aerospace Lab](https://www.tamtam.ai/c/onera-the-french-aerospace-lab) (onera.fr)<br>Researching future aerospace and defense challenges, contributing to industry competitiveness through expertise in all related disciplines and technologies. | Aviation and Aerospace Component Manufacturing | 🇫🇷 Palaiseau | 2,097 | 1946 |
| 5 | [ASN](https://www.tamtam.ai/c/asn) (asn.com)<br>Designs, installs, and maintains global optical submarine cable systems for telecom, content providers, and offshore oil and gas industries. | Telecommunications | 🇫🇷 Les Ulis | 1,717 | 1994 |
| 6 | [Menard](https://www.tamtam.ai/c/menard) (menard-group.com)<br>A global leader in ground improvement works using innovative technologies to optimize geotechnical conditions for various infrastructure projects worldwide | Construction | 🇫🇷 Orsay | 1,590 |  |
| 7 | [TechnicAtome](https://www.tamtam.ai/c/technicatome) (technicatome.com)<br>Specialized in compact nuclear reactor design, construction, and maintenance for various sectors including naval propulsion, research, medicine, and energy | Defense and Space Manufacturing | 🇫🇷 Villiers-le-Bâcle | 1,467 | 1972 |
| 8 | [UTAC](https://www.tamtam.ai/c/utac) (utac.com)<br>Advancing mobility industry towards safer, cleaner future. Provides large range of services to bring vehicles to market. | Motor Vehicle Manufacturing | 🇫🇷 Linas | 1,249 |  |
| 9 | [CENTRE HOSPITALIER SUD FRANCILIEN](https://www.tamtam.ai/c/centre-hospitalier-sud-francilien) (chsf.fr)<br>Public healthcare institution serving one million people in southern Île-de-France, providing medical services and hospital care to the community. | Hospitals and Health Care | 🇫🇷 Corbeil-Essonnes | 1,219 |  |
| 10 | [Eurostyle Systems](https://www.tamtam.ai/c/eurostyle-systems-les-ulis) (eurostyle-systems.fr)<br>Design and production of industrial solutions specializing in high-precision plastics processing and leather materials for global automotive markets across fourteen production sites. | Manufacturing | 🇫🇷 Les Ulis | 1,158 | 1964 |
| 11 | [HORIBA for Materials](https://www.tamtam.ai/c/horiba-for-materials) (horiba.com)<br>Researching, developing new materials, improving manufacturing, and implementing recycling solutions for sustainability across the material supply chain. | Research Services | 🇫🇷 Palaiseau | 1,053 |  |
| 12 | [Sebia](https://www.tamtam.ai/c/sebia) (sebia.com)<br>Global specialty in vitro diagnostic leader for screening and monitoring various diseases, including oncology, diabetes, and autoimmunity. | Medical Equipment Manufacturing | 🇫🇷 Lisses | 1,018 | 1967 |
| 13 | [Télécom Paris](https://www.tamtam.ai/c/telecom-paris) (telecom-paris.fr)<br>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 | Higher Education | 🇫🇷 Palaiseau | 953 | 1878 |
| 14 | [Infovista](https://www.tamtam.ai/c/infovista) (infovista.com)<br>Empowers service providers and enterprises with data-driven solutions for optimizing network performance, enhancing customer experience, and driving business success. | Software Development | 🇫🇷 Massy | 834 | 1995 |
| 15 | [L-Acoustics](https://www.tamtam.ai/c/l-acoustics) (l-acoustics.com)<br>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 | Appliances, Electrical, and Electronics Manufacturing | 🇫🇷 Marcoussis | 700 | 1984 |
| 16 | [Horoquartz](https://www.tamtam.ai/c/horoquartz) (horoquartz.com)<br>Provides integrated solutions for workforce management, planning optimization, activity tracking, access control, and identity management, serving over 5000 clients globally. | Software Development | 🇫🇷 Massy | 568 | 1971 |
| 17 | [Vernet Group](https://www.tamtam.ai/c/vernet-group) (vernet-group.com)<br>Family company, world leader in thermal regulation, designing and manufacturing thermostats and thermostatic elements for automotive, heating, and plumbing industries. | Mechanical Or Industrial Engineering | 🇫🇷 Ollainville | 418 | 1927 |
| 18 | [Synchrotron SOLEIL](https://www.tamtam.ai/c/synchrotron-soleil) (synchrotron-soleil.fr)<br>Third generation synchrotron providing advanced experimental facilities for material geometry and properties research, serving diverse scientific users worldwide. | Research Services | 🇫🇷 Gif-sur-Yvette | 403 | 2001 |
| 19 | [Pasqal](https://www.tamtam.ai/c/pasqal) (pasqal.com)<br>The company specializes in building programmable quantum simulators and computers using neutral atoms in optical tweezers for quantum information processing | IT Services and IT Consulting | 🇫🇷 Palaiseau | 297 | 2019 |
| 20 | [MyUnisoft](https://www.tamtam.ai/c/myunisoft) (myu.fr)<br>Develops a collaborative cloud platform for accounting firms, simplifying daily tasks, automating workflows, and enhancing client relationships with integrated financial management and e-invoicing compliance. | Accounting | 🇫🇷 Massy | 242 | 2018 |
| 21 | [Eurostyle Systems](https://www.tamtam.ai/c/eurostyle-systems) (eurostyle-systems.fr)<br>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 | Motor Vehicle Manufacturing | 🇫🇷 Les Ulis | 234 | 1964 |
| 22 | [Exotrail](https://www.tamtam.ai/c/exotrail) (exotrail.com)<br>Develops and operates propulsion systems, mission simulation software, and orbital transfer vehicles for efficient, sustainable space mobility, enabling telecommunication, Earth observation, space exploration. | Defense and Space Manufacturing | 🇫🇷 Massy | 215 | 2015 |
| 23 | [PMC Isochem](https://www.tamtam.ai/c/pmc-isochem) (pmcisochem.fr)<br>Custom manufacturing of APIs, intermediates, and excipients with drug delivery solutions including Vitamin E TPGS and amino acid polymers for pharmaceuticals. | Chemical Manufacturing | 🇫🇷 Vert-le-Petit | 215 | 2017 |
| 24 | [PCAS](https://www.tamtam.ai/c/pcas) (seqens.com)<br>Develops and produces complex molecules using advanced technologies for global leaders in Life Sciences and Innovative Technologies. Part of a larger international group. | Chemical Manufacturing | 🇫🇷 Longjumeau | 213 | 1962 |
| 25 | [UMS - United Monolithic Semiconductors](https://www.tamtam.ai/c/ums-united-monolithic-semiconductors) (ums-rf.com)<br>Designs and manufactures GaAs and GaN based RF and millimeter-wave integrated circuits and provides advanced foundry services for critical applications. | Semiconductor Manufacturing | 🇫🇷 Villebon-sur-Yvette | 210 | 1996 |
| 26 | [Anton Paar France](https://www.tamtam.ai/c/anton-paar-france) (anton-paar.com)<br>Sales of measurement and laboratory instruments for density, concentration, rheometry, and CO2 analysis serving industry and research sectors. | Measuring and Control Instrument Manufacturing | 🇫🇷 Les Ulis | 201 | 2001 |
| 27 | [SOPHYSA](https://www.tamtam.ai/c/sophysa) (sophysa.com)<br>Develops neurosurgical implants, including adjustable valves for hydrocephalus and intracranial pressure monitoring systems, offering advanced solutions for neurological conditions. | Medical Equipment Manufacturing | 🇫🇷 Orsay | 195 | 1976 |
| 28 | [Eurobio Scientific FR](https://www.tamtam.ai/c/eurobio-scientific-fr) (eurobio-scientific.com)<br>Develops, manufactures, and commercializes in-vitro diagnostic products for hospitals and private medical biology laboratories, specializing in transplantation, infectious diseases, and life sciences. | Biotechnology Research | 🇫🇷 Les Ulis | 193 |  |
| 29 | [ADALTRA](https://www.tamtam.ai/c/adaltra) (adaltra.fr)<br>Specializing in communication systems for various environments such as offices, hotels, hospitals, airports, stadiums, and more, our solutions are designed by CAE GROUPE | Manufacturing | 🇫🇷 Massy | 182 |  |
| 30 | [Sefi-Intrafor](https://www.tamtam.ai/c/sefi-intrafor) (fayat.com)<br>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 | Construction | 🇫🇷 Grigny | 181 | 1965 |

## 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)
- [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)
- [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

- [Companies with in-house R&D in France](https://www.tamtam.ai/l/r-and-d-companies-france) (8,750)
- [Companies with in-house R&D in Île-de-France](https://www.tamtam.ai/l/r-and-d-companies-ile-de-france) (2,695)
- [Companies with in-house R&D in Auvergne-Rhône-Alpes](https://www.tamtam.ai/l/r-and-d-companies-auvergne-rhone-alpes) (1,460)
- [Companies with in-house R&D in Occitanie](https://www.tamtam.ai/l/r-and-d-companies-occitanie) (680)
- [Companies with in-house R&D in Grand Est](https://www.tamtam.ai/l/r-and-d-companies-grand-est) (640)
- [Companies with in-house R&D in Provence-Alpes-Côte d'Azur](https://www.tamtam.ai/l/r-and-d-companies-provence-alpes-cote-dazur) (613)
- [Companies with in-house R&D in Nouvelle-Aquitaine](https://www.tamtam.ai/l/r-and-d-companies-nouvelle-aquitaine) (566)
- [Companies with in-house R&D in the Hauts-de-Seine department](https://www.tamtam.ai/l/r-and-d-companies-hauts-de-seine) (510)
- [Companies with in-house R&D in the Rhône department](https://www.tamtam.ai/l/r-and-d-companies-rhone) (509)
- [Companies with in-house R&D in Pays de la Loire](https://www.tamtam.ai/l/r-and-d-companies-pays-de-la-loire) (480)
- [Companies with in-house R&D in Hauts-de-France](https://www.tamtam.ai/l/r-and-d-companies-hauts-de-france) (410)
- [Companies with in-house R&D in Brittany](https://www.tamtam.ai/l/r-and-d-companies-brittany) (366)
- [Companies with in-house R&D in the Haute-Garonne department](https://www.tamtam.ai/l/r-and-d-companies-haute-garonne) (323)
- [Companies with in-house R&D in the Bouches-du-Rhône department](https://www.tamtam.ai/l/r-and-d-companies-bouches-du-rhone) (321)
- [Companies with in-house R&D in the Isère department](https://www.tamtam.ai/l/r-and-d-companies-isere) (304)
- [Companies with in-house R&D in Bourgogne-Franche-Comté](https://www.tamtam.ai/l/r-and-d-companies-bourgogne-franche-comte) (261)
- [Companies with in-house R&D in the Nord department](https://www.tamtam.ai/l/r-and-d-companies-nord) (237)
- [Companies with in-house R&D in Normandy](https://www.tamtam.ai/l/r-and-d-companies-normandy) (227)
- [Companies with in-house R&D in the Gironde department](https://www.tamtam.ai/l/r-and-d-companies-gironde) (225)
- [Companies with in-house R&D in the Loire-Atlantique department](https://www.tamtam.ai/l/r-and-d-companies-loire-atlantique) (207)
- [Companies with in-house R&D in Centre-Val de Loire](https://www.tamtam.ai/l/r-and-d-companies-centre-val-de-loire) (195)
- [Companies with in-house R&D in Paris](https://www.tamtam.ai/l/r-and-d-companies-paris) (1,249)
- [Companies with in-house R&D in Lyon](https://www.tamtam.ai/l/r-and-d-companies-lyon) (192)
- [Companies with in-house R&D in Toulouse](https://www.tamtam.ai/l/r-and-d-companies-toulouse) (172)

---

Source: https://www.tamtam.ai/l/r-and-d-companies-essonne