These companies in Hauts-de-Seine are primarily large consulting firms, specializing in IT, engineering, and business services. Notable examples include ALTEN, which provides engineering and IT services, and Devoteam, an AI-driven tech consulting firm. Forvis Mazars Group offers audit, tax, and advisory services, while Apave specializes in technical and environmental risk management. Assystem focuses on nuclear engineering and energy transition, and TRIGO provides quality solutions for automotive, aerospace, and transport industries.
The headquarters of these major firms are concentrated in a few key cities within Hauts-de-Seine. Boulogne-Billancourt, Neuilly-sur-Seine, and Levallois-Perret emerge as central hubs, hosting a significant number of these large employers. A common founding era is also observed, with many of these companies, such as ALTEN and Astek, established around the late 1980s.
| # | Company | Employees | |||
|---|---|---|---|---|---|
| 1 | 38,710 | ||||
| 2 |
Altrancapgemini-engineering.com
Altran, now Capgemini Engineering, offers engineering services Follow them on LinkedIn for updates and insights |
11,652 | |||
| 3 |
Devoteamdevoteam.com
AI-driven tech consulting firm specializing in cloud platforms, cyber, data, and sustainability, guiding businesses through sustainable digital transformation to deliver value. |
10,274 | |||
| 4 | 9,778 | ||||
| 5 |
Forvis Mazars Groupforvismazars.com
International partnership delivering audit, tax, and advisory services across one hundred countries and territories through an integrated global professional services network. |
9,534 | |||
| 6 |
Assystemassystem.com
Independent nuclear engineering company accelerating energy transition, developing nuclear and renewable energies, power grids, hydrogen projects, and low-carbon transport. |
8,143 | |||
| 7 |
Astekastekgroup.fr
Supports clients with high-value service, deep technical expertise across technology, operations, and engineering, focusing on sustainable digital transformation with humans at the core. |
6,035 | |||
| 8 |
TRIGOtrigo-group.com
Provides comprehensive quality solutions and management services for automotive, aerospace, and transport industries, addressing supply chain challenges globally with local expertise. |
5,771 | |||
| 9 |
Vulcain Engineering Groupvulcain-eng.com
Provides engineering consulting and project solutions for energy and environmental sectors, delivering technical assistance, expertise, and project management globally. |
5,234 | |||
| 10 |
Synergie Francesynergie.fr
French leader in HR services: recruitment, training, and HR consulting Providing solutions in various sectors, emphasizing proximity, performance, and diversity |
4,804 | |||
| 11 |
OPENopen.global
Supports large companies and public organizations in digital transformation, focusing on technological performance, sovereignty, digital sobriety, and scaling innovations with advanced solutions. |
4,705 | |||
| 12 |
BNP Paribas Real Estatebnpparibas.com
Offers comprehensive real estate services including property development, transactions, consulting, valuation, and property management across Europe, the Middle East, and Asia. |
4,173 | |||
| 13 |
PwC Francepwc.fr
Offers consulting, audit, legal, and tax expertise, blending technology with multidisciplinary knowledge to accelerate sustainable business transformation for organizations. |
4,109 | |||
| 14 |
Scalianscalian.com
A global company founded in 1989 with 3 business lines focusing on Digital Transformation, Digital Systems, and Operations Performance across various countries |
4,098 | |||
| 15 |
Leytonleyton.com
International consulting firm helps businesses leverage financial incentives for growth and long-lasting performance by simplifying access to complex benefits. |
3,243 | |||
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 | 3,016 | ||||
| 17 |
SE Advisory Servicesseadvisoryservices.com
Helps organizations achieve sustainability, energy, and digitalization goals through expertise, global implementation, and AI-powered software, turning challenges into advantages. |
2,948 | |||
| 18 |
Grant-Thornton Francegrantthornton.fr
Provides audit, financial advisory, operational consulting, legal and tax advice, and sustainable transformation services to French businesses. |
2,342 | |||
| 19 |
Apsideapside.com
Provides consulting, engineering in Information Systems, Technical and Scientific Computing, Automotive and Financial Engineering, for large French and European groups. |
2,300 | |||
| 20 |
Ing茅ropingerop.fr
An independent engineering company with expertise in infrastructure, transportation, water, environment, energy, and industrial facilities in over 70 countries |
2,268 | |||
| 21 | 2,075 | ||||
| 22 |
Aymingayming.com
Partners with businesses, institutions to unlock lasting value. Translates policy into opportunities, manages growth transformation. Specializes in innovation, HR, taxes across 14 countries. Delivers tangible results beyond consulting. |
1,947 | |||
| 23 |
Infotelinfotel.com
Provides IT and digital transformation consulting for large enterprises, focusing on strategic design, technological expertise, and agile development, from conception to implementation. |
1,894 | |||
| 24 |
Extiaextia-group.com
Offers IT consulting services across various sectors, focusing on employee well-being to drive project success and client performance with a collaborative approach. |
1,881 | |||
| 25 |
Davidson consultingdavidson.fr
A management consulting and technology company with over 2,000 employees, expanding internationally with a focus on employee well-being and creativity |
1,843 | |||
| 26 |
Sofrecomsofrecom.com
Advises, guides, and supports telecommunications players' digital transformation and green transition, offering business, network, and IT consulting for improved operational performance. |
1,469 | |||
| 27 |
ProductLife Groupproductlifegroup.com
Global service provider in Life Sciences, delivering end-to-end consulting and outsourcing services across the entire product lifecycle for various sectors. |
1,469 | |||
| 28 | 1,460 | ||||
| 29 |
Cegos Francecegos.fr
Provides extensive professional training and development programs across management, leadership, HR, marketing, and project management internationally with expert consultants. |
1,259 | |||
| 30 | 1,213 | ||||
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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 12, 2026.
More company lists in the Hauts-de-Seine department
- The largest companies in the Hauts-de-Seine department 5,160
- Multinational companies in the Hauts-de-Seine department 1,231
- IT services companies in the Hauts-de-Seine department 737
- IT Services and IT Consulting companies in the Hauts-de-Seine department 706
- Professional services firms in the Hauts-de-Seine department 629
- Companies with in-house R&D in the Hauts-de-Seine department 510
- SaaS companies in the Hauts-de-Seine department 389
- Business Consulting and Services companies in the Hauts-de-Seine department 304
- Software Development companies in the Hauts-de-Seine department 301
- Retail chains in the Hauts-de-Seine department 292
- Manufacturers in the Hauts-de-Seine department 285
- Advertising Services companies in the Hauts-de-Seine department 281
- Marketing and communications agencies in the Hauts-de-Seine department 235
- Subscription businesses in the Hauts-de-Seine department 228
- Hardware manufacturers in the Hauts-de-Seine department 199
- Financial services firms in the Hauts-de-Seine department 198
- Companies with a mobile app in the Hauts-de-Seine department 189
- Critical infrastructure operators in the Hauts-de-Seine department 169
- AI companies in the Hauts-de-Seine department 159
- Education providers in the Hauts-de-Seine department 159
- Cybersecurity companies in the Hauts-de-Seine department 154
- Distributors and wholesalers in the Hauts-de-Seine department 154
- Recruitment and staffing agencies in the Hauts-de-Seine department 152
- Energy companies in the Hauts-de-Seine department 144
The same list elsewhere in France
- Consulting firms in France 4,251
- Consulting firms in 脦le-de-France 2,408
- Consulting firms in Auvergne-Rh么ne-Alpes 412
- Consulting firms in the Rh么ne department 242
- Consulting firms in Occitanie 236
- Consulting firms in Provence-Alpes-C么te d'Azur 233
- Consulting firms in Nouvelle-Aquitaine 166
- Consulting firms in Grand Est 165
- Consulting firms in Hauts-de-France 161
- Consulting firms in Pays de la Loire 160
- Consulting firms in the Haute-Garonne department 145
- Consulting firms in the Bouches-du-Rh么ne department 129
- Consulting firms in the Nord department 115
- Consulting firms in Brittany 99
- Consulting firms in the Loire-Atlantique department 94
- Consulting firms in the Gironde department 82
- Consulting firms in the Yvelines department 72
- Consulting firms in the Is猫re department 57
- Consulting firms in Paris 1,532
- Consulting firms in Lyon 163
- Consulting firms in Toulouse 98
- Consulting firms in Boulogne-Billancourt 88
- Consulting firms in Levallois-Perret 83
- Consulting firms in Neuilly-sur-Seine 73