# 30 leading critical infrastructure operators in the Seine-Saint-Denis department
Tamtam tracks 53 critical infrastructure operators headquartered in the Seine-Saint-Denis department. This list ranks the 30 largest by number of employees on LinkedIn, led by Veolia, SNCF Réseau and SNCF Voyageurs. Their median headcount is 645. Half of them were founded in 2000 or later. The most common headquarters are Saint-Denis (10), Aubervilliers (6) and Montreuil (5).
This selection of critical infrastructure operators in Seine-Saint-Denis includes large groups and public entities. Veolia, with over 50,000 employees, specializes in environmental services like water, waste, and energy solutions. SNCF Réseau manages national railway infrastructure, while SNCF Voyageurs handles passenger transportation. GRDF operates Europe's largest gas distribution network, and BNP Paribas - Securities Services provides asset servicing solutions to financial markets. ACOSS supports employers and entrepreneurs in social protection financing.
A notable pattern is the strong presence of companies in essential public services and utilities. Environmental services, rail transportation, and government administration are particularly well-represented. Many of these organizations, such as Veolia and Generali France, have long histories, indicating established operations within the department.
🇫🇷 Seine-Saint-Denis · 30 companies · Updated Nov 11, 2026
| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Veolia](https://www.tamtam.ai/c/veolia-aubervilliers) (veolia.com)
Works to build environmental security, cleans up pollution, reduces carbon emissions, and regenerates resources through water, waste, and energy solutions. | Environmental Services | 🇫🇷 Aubervilliers | 50,280 | 1853 |
| 2 | [SNCF Réseau](https://www.tamtam.ai/c/sncf-reseau) (sncf-reseau.fr)
public entity managing national railway infrastructure, unifying previous services, ensuring clear governance, and coordinating with railway operator SNCF Mobilités. | Rail Transportation | 🇫🇷 Saint-Denis | 23,115 | 2015 |
| 3 | [SNCF Voyageurs](https://www.tamtam.ai/c/sncf-voyageurs) (sncf-voyageurs.com)
SNCF Voyageurs is a subsidiary of the SNCF Group responsible for passenger transportation on the French national railway network | Rail Transportation | 🇫🇷 Saint-Denis | 18,564 | 2020 |
| 4 | [Veolia \| Water Tech](https://www.tamtam.ai/c/veolia-water-tech) (veoliawatertechnologies.com)
Provides global water technology expertise, ensuring performance, sustainability, and resource protection for communities and industries through advanced solutions and services. | Environmental Services | 🇫🇷 Aubervilliers | 13,064 | |
| 5 | [GRDF](https://www.tamtam.ai/c/grdf) (grdf.fr)
Manages Europe's largest gas distribution network, delivering natural and renewable gases to nearly 11 million customers in France, supporting energy transition. | Oil and Gas | 🇫🇷 Saint-Denis | 7,313 | 2008 |
| 6 | [BNP Paribas - Securities Services](https://www.tamtam.ai/c/bnp-paribas-securities-services) (cib.bnpparibas)
Provides multi-asset post-trade, asset servicing solutions to financial market participants, corporates, and issuers, with an extensive global custody network. | Financial Services | 🇫🇷 Pantin | 6,196 | |
| 7 | [Veolia \| France](https://www.tamtam.ai/c/veolia-france) (veolia.fr)
Provides specialized services for water management, waste treatment, and energy recovery to help cities and industries preserve, access, and renew essential resources. | Environmental Services | 🇫🇷 Aubervilliers | 6,110 | 1853 |
| 8 | [ACOSS](https://www.tamtam.ai/c/acoss) (linkedin.com)
A national organization supports employers and entrepreneurs by advising, informing, and streamlining services, ensuring social protection financing, and promoting responsibility, solidarity, and equity | Government Administration | 🇫🇷 Montreuil | 3,000 | |
| 9 | [Agence Régionale de Santé Ile-de-France](https://www.tamtam.ai/c/agence-regionale-de-sante-ile-de-france) (linktr.ee)
Implements regional health policy, covering prevention, care, and medico-social support, developed in consultation with professionals and users for efficiency and transparency. | Government Administration | 🇫🇷 Saint-Denis | 2,332 | 2010 |
| 10 | [Generali France](https://www.tamtam.ai/c/generali-france) (generali.fr)
Protecting and ensuring the lives of individuals | Insurance | 🇫🇷 Saint-Denis | 1,677 | 1832 |
| 11 | [Société des grands projets](https://www.tamtam.ai/c/societe-des-grands-projets) (societedesgrandsprojets.fr)
Development and management of decarbonized transport projects including new metro lines and regional express services to improve daily mobility. | Urban Transit Services | 🇫🇷 Saint-Denis | 1,367 | |
| 12 | [Urssaf Ile-de-France](https://www.tamtam.ai/c/urssaf-ile-de-france) (lasecurecrute.fr)
Collection and redistribution of social security contributions ensuring workers' social protection and supporting entrepreneurs with compliance and service. | Government Administration | 🇫🇷 Montreuil | 1,142 | |
| 13 | [GEH - Groupe Europe Handling](https://www.tamtam.ai/c/geh-groupe-europe-handling) (geh.aero)
Provides innovative, efficient airport services, encompassing passenger and baggage handling, ground support, traffic operations, cargo management, and maintenance for airlines worldwide since 1994. | Airlines and Aviation | 🇫🇷 Tremblay-en-France | 911 | 1994 |
| 14 | [DHL Express France](https://www.tamtam.ai/c/dhl-express-france) (dhlexpress.fr)
Global leader in international express transport providing carbon-conscious logistics, parcel delivery, and supply chain solutions for business and individual customers through extensive networks. | Transportation, Logistics, Supply Chain and Storage | 🇫🇷 Le Bourget | 828 | 1969 |
| 15 | [Hub One](https://www.tamtam.ai/c/hub-one) (hubone.fr)
Hub One, a technology group, provides digital evolution services for businesses in various sectors They offer connectivity solutions for communication, networking, and mobility | Telecommunications | 🇫🇷 Tremblay-en-France | 645 | 2001 |
| 16 | [SNCF Voyageurs Matériel](https://www.tamtam.ai/c/sncf-voyageurs-materiel) (sncf-voyageurs.com)
Manages maintenance for nearly 17,000 rolling stock units. Provides high-level industrial performance, ensuring safety, quality, and technical expertise for internal and external clients. | Rail Transportation | 🇫🇷 Saint-Denis | 606 | |
| 17 | [DB Cargo France](https://www.tamtam.ai/c/db-cargo-france) (dbcargo.com)
Provides diverse rail freight solutions from single wagons to full trains, including combined transport across France and to bordering countries for various goods. | Rail Transportation | 🇫🇷 Aubervilliers | 527 | 2005 |
| 18 | [GROUPE CORIANCE](https://www.tamtam.ai/c/groupe-coriance) (groupe-coriance.fr)
Providing high-performance and cost-effective energy solutions while minimizing environmental impact, specializing in renewable energy sources like geothermal, biomass, and cogeneration | Environmental Services | 🇫🇷 Noisy-le-Grand | 509 | 1998 |
| 19 | [Grand Paris Express](https://www.tamtam.ai/c/grand-paris-express) (grandparisexpress.fr)
Public organization creating the new Grand Paris automated metro, responsible for designing, developing, and building the network's infrastructure and stations | Urban Transit Services | 🇫🇷 Saint-Denis | 454 | 2011 |
| 20 | [Crédit Agricole La Réunion - Mayotte](https://www.tamtam.ai/c/credit-agricole-la-reunion-mayotte) (credit-agricole.fr)
A mutual bank supporting individuals, professionals, farmers, and associations with their projects in Réunion and Mayotte for over 72 years | Banking | 🇫🇷 Saint-Denis | 442 | 1950 |
| 21 | [Veolia \| Énergie & Décarbonation](https://www.tamtam.ai/c/veolia-energie-and-decarbonation) (veolia.fr)
Provides energy audits, renewable production, smart cooling networks, and performance optimization to ensure sovereignty and environmental footprint reduction for industries and local territories. | Environmental Services | 🇫🇷 Aubervilliers | 429 | |
| 22 | [UGECAM Ile-de-France](https://www.tamtam.ai/c/ugecam-ile-de-france) (groupe-ugecam.fr)
Non-profit organization providing comprehensive health and social care services, supporting rehabilitation and reintegration for individuals with disabilities across various age groups and needs. | Hospitals and Health Care | 🇫🇷 Montreuil | 419 | 2000 |
| 23 | [ASL Airlines France](https://www.tamtam.ai/c/asl-airlines-france) (aslairlines.fr)
Provides passenger flights for tour operators, regular international routes, VIP charters, and dedicated aircraft. Also offers express and on-demand cargo services. | Airlines and Aviation | 🇫🇷 Tremblay-en-France | 394 | 2000 |
| 24 | [CENTRE HOSPITALIER DE MONTREUIL HOPITAL ANDRE GREGOIRE](https://www.tamtam.ai/c/centre-hospitalier-de-montreuil-hopital-andre-gregoire) (ght-gpne.fr)
Medical practice company based in Montreuil, France, providing a range of healthcare services at Hôpital André Grégoire | Medical Practices | 🇫🇷 Montreuil | 388 | |
| 25 | [Netcom Group](https://www.tamtam.ai/c/netcom-group) (netcom-group.fr)
Operator providing fixed, mobile, and internet solutions for businesses, emphasizing customer satisfaction, transparency, and eco-responsible products. | Telecommunications | 🇫🇷 Pantin | 302 | 2004 |
| 26 | [GHT Grand Paris Nord-Est](https://www.tamtam.ai/c/ght-grand-paris-nord-est) (ght-gpne.fr)
Three hospitals in Seine-Saint-Denis providing specialized, teaching, and research healthcare services with over 6000 professionals ensuring coordinated, quality patient care. | Hospitals and Health Care | 🇫🇷 Montfermeil | 297 | 2016 |
| 27 | [Centre Hospitalier de Saint-Denis](https://www.tamtam.ai/c/centre-hospitalier-de-saint-denis) (ch-stdenis.fr)
Public hospital offering medical care without discrimination, with a focus on multicultural patient care Provides various medical specialties, including emergency services and perinatal care | Hospitals and Health Care | 🇫🇷 Saint-Denis | 293 | |
| 28 | [LOOMIS France](https://www.tamtam.ai/c/loomis-france) (fr.loomis.com)
Leader in cash management and security services operating the largest value logistics network, offering innovative solutions to accelerate cash flow and availability worldwide | Truck Transportation | 🇫🇷 Aubervilliers | 285 | 1992 |
| 29 | [Apria RSA](https://www.tamtam.ai/c/apria-rsa) (apriarsa.fr)
Apria RSA is a health and insurance management organization with expertise in obligatory health insurance, project management, collective solutions, and customer relations services | Insurance | 🇫🇷 Montreuil | 195 | |
| 30 | [Clinique de l'Estrée - GROUPE ELSAN](https://www.tamtam.ai/c/clinique-de-l-estree-groupe-elsan) (elsan.care)
The company is a medical facility offering a wide range of services including surgery, maternity, medicine, dialysis, chemotherapy, and post-care treatments | Hospitals and Health Care | 🇫🇷 Stains | 153 | 1956 |
## 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 Seine-Saint-Denis department
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- [Consulting firms in the Seine-Saint-Denis department](https://www.tamtam.ai/l/consulting-firms-seine-saint-denis) (44)
- [Companies with a mobile app in the Seine-Saint-Denis department](https://www.tamtam.ai/l/companies-with-mobile-app-seine-saint-denis) (44)
- [Construction companies in the Seine-Saint-Denis department](https://www.tamtam.ai/l/construction-companies-seine-saint-denis) (44)
- [Logistics companies in the Seine-Saint-Denis department](https://www.tamtam.ai/l/logistics-companies-seine-saint-denis) (40)
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## The same list elsewhere in France
- [Critical infrastructure operators in France](https://www.tamtam.ai/l/critical-infrastructure-operators-france) (2,721)
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- [Critical infrastructure operators in Hauts-de-France](https://www.tamtam.ai/l/critical-infrastructure-operators-hauts-de-france) (174)
- [Critical infrastructure operators in the Hauts-de-Seine department](https://www.tamtam.ai/l/critical-infrastructure-operators-hauts-de-seine) (169)
- [Critical infrastructure operators in Pays de la Loire](https://www.tamtam.ai/l/critical-infrastructure-operators-pays-de-la-loire) (127)
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- [Critical infrastructure operators in the Rhône department](https://www.tamtam.ai/l/critical-infrastructure-operators-rhone) (94)
- [Critical infrastructure operators in Centre-Val de Loire](https://www.tamtam.ai/l/critical-infrastructure-operators-centre-val-de-loire) (87)
- [Critical infrastructure operators in the Nord department](https://www.tamtam.ai/l/critical-infrastructure-operators-nord) (87)
- [Critical infrastructure operators in Bourgogne-Franche-Comté](https://www.tamtam.ai/l/critical-infrastructure-operators-bourgogne-franche-comte) (76)
- [Critical infrastructure operators in the Haute-Garonne department](https://www.tamtam.ai/l/critical-infrastructure-operators-haute-garonne) (64)
- [Critical infrastructure operators in the Gironde department](https://www.tamtam.ai/l/critical-infrastructure-operators-gironde) (63)
- [Critical infrastructure operators in the Loire-Atlantique department](https://www.tamtam.ai/l/critical-infrastructure-operators-loire-atlantique) (59)
- [Critical infrastructure operators in the Hérault department](https://www.tamtam.ai/l/critical-infrastructure-operators-herault) (57)
- [Critical infrastructure operators in the Seine-Maritime department](https://www.tamtam.ai/l/critical-infrastructure-operators-seine-maritime) (46)
- [Critical infrastructure operators in the Ille-et-Vilaine department](https://www.tamtam.ai/l/critical-infrastructure-operators-ille-et-vilaine) (45)
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Source: https://www.tamtam.ai/l/critical-infrastructure-operators-seine-saint-denis