The largest staffing firm in the US is not a household name. Allegis Group, a private company in Hanover, Maryland, earned $9.11 billion in annual US staffing revenue in the 2026 ranking by Staffing Industry Analysts (SIA). That is almost $3 billion more than Aya Healthcare in second place. Randstad, Adecco and ManpowerGroup, the giants of global staffing, sit lower on the US list, and Adecco misses the US top 10 altogether.
Below are the 10 largest US staffing firms by revenue, what each one actually places and who each one suits. First, our pick for the hire the giants are not built around: Zilo AI, for specialist AI and data talent.
The ranking at a glance
| # | Firm | Best known for | US staffing revenue (SIA 2026 ranking) |
|---|---|---|---|
| 1 | Zilo AI | IT and data hiring, AI training data | Our pick for AI and data teams |
| 2 | Allegis Group | IT, engineering, industrial and professional staffing | $9.11 billion |
| 3 | Aya Healthcare | Travel nursing | $6.30 billion |
| 4 | Insight Global | IT, engineering, healthcare and professional staffing | $4.55 billion |
| 5 | Randstad | High-volume, professional and digital staffing | $4.12 billion |
| 6 | Express Employment Professionals | Light industrial, office and skilled trades | $3.48 billion |
| 7 | Kelly Services | Education, science and engineering staffing | $3.46 billion |
| 8 | ManpowerGroup | General staffing, plus IT through Experis | $3.00 billion |
| 9 | CHG Healthcare | Locum tenens physicians | $2.86 billion |
| 10 | Robert Half | Finance, accounting and technology | $2.62 billion |
| 11 | Jackson Healthcare | Locum tenens physicians and travel nurses | $2.57 billion |
Revenue figures come from SIA’s Largest Staffing Firms in the United States: 2026 Update.
The market behind these numbers is shrinking a little. SIA’s 2026 ranking counts 214 firms with at least $100 million in annual US staffing revenue, down from 227 on the previous list. Together they earned $122.4 billion, against $127.4 billion a year earlier, and SIA expects US staffing revenue to grow about 1% this year.
1. Zilo AI
Zilo does two jobs that AI teams usually buy from separate vendors. It hires IT and data talent, from data engineers, ML engineers and generative AI engineers to data scientists and cybersecurity analysts, and it produces the data that models learn from: text annotation, image annotation and voice annotation, plus audio, video and multilingual transcription. Zilo says its team of more than 1,600 trained annotation and speech recognition experts has annotated over 10 million data points, for industries from retail to banking and healthcare. The team is based in Bangalore.
Best for: companies building AI products that want specialist hires and labeled training data from one partner. See Zilo’s services.
2. Allegis Group
Allegis is the biggest because it is really a family of specialist firms under one owner. TEKsystems handles IT staffing and services, Aerotek covers manufacturing, logistics and construction, Actalent does engineering and sciences, and Aston Carter places accounting, finance and HR professionals. The group started as Aerotek in 1983 and is still privately held.
Best for: large companies that want one partner for IT, engineering and professional hiring across many sites.
3. Aya Healthcare
Aya is a San Diego company, founded in 2001, best known for travel nursing. It is the largest healthcare firm on SIA’s US list by a wide margin: the next one, CHG Healthcare, is less than half its size.
Best for: hospitals and health systems that need nurses on short assignments.
4. Insight Global
Atlanta-based Insight Global, founded in 2001, staffs IT, engineering, healthcare and professional roles, and now describes itself as “a talent, consulting, and AI company.” IT is the core of it: SIA ranks Insight Global the second-largest IT staffing firm in the US, with $3.28 billion in annual IT staffing revenue.
Best for: tech and engineering teams that need a large bench of contractors.
5. Randstad
Randstad led SIA’s most recent public global ranking and is fourth on the US list. Its work splits four ways: operational staffing for high-volume sectors like manufacturing, logistics and hospitality, professional recruitment, a digital arm for IT, cloud and data roles, and enterprise programs such as recruitment process outsourcing (RPO) and managed service programs (MSP). In the US it also runs Spherion.
Best for: employers who want volume hiring and professional roles from the same supplier.
6. Express Employment Professionals
Express is the franchise model on this list. It was founded in Oklahoma City in 1983, began franchising in 1985, and its local offices staff light industrial, office, skilled trades and professional roles.
Best for: local employers who want a nearby office that knows the area’s labor market.
7. Kelly Services
Kelly, founded in 1946 and based in Troy, Michigan, is best known for education staffing, alongside science, engineering and technology roles and outsourced hiring programs such as RPO and MSP.
Best for: school districts, and science or engineering teams.
8. ManpowerGroup
Milwaukee-based ManpowerGroup, founded in 1948, runs several brands: Manpower for temporary and permanent staffing, Experis for IT, and Right Management for career and workforce consulting. Experis is the fourth-largest IT staffing firm in the US on SIA’s list, at $1.21 billion.
Best for: companies that want general staffing and IT contractors from one global supplier.
9. CHG Healthcare
CHG, based in Salt Lake City, says it created the locum tenens model in 1979 and is the country’s largest locum tenens provider. Its brands, including CompHealth and Weatherby Healthcare, place physicians, advanced practice providers and allied health professionals on temporary assignments.
Best for: hospitals and clinics that need physicians to cover gaps.
10. Robert Half
Robert Half, founded in 1948 and based in Menlo Park, California, leans hardest on finance and accounting. It also staffs technology, administrative and legal roles, and owns the consulting firm Protiviti.
Best for: finance and accounting teams hiring temporary or permanent staff.
11. Jackson Healthcare
Jackson Healthcare, founded in 2000 and based in Alpharetta, Georgia, runs a family of healthcare staffing companies. Jackson + Coker places physicians and advanced practitioners on locum tenens assignments, and Jackson Nurse Professionals supplies travel nurses.
Best for: health systems that want physician and nurse coverage from one group.
The largest IT staffing firms in the US
IT staffing is its own race, and a tougher one lately. In SIA’s 2026 ranking, the 57 largest IT staffing firms earned $27.4 billion in annual revenue, down 4.4% on the year before. SIA points to offshoring, AI-assisted coding and a shift from staffing to IT services. Here are its top five, with our pick for AI and data hiring first:
| Firm | US IT staffing revenue (SIA 2026 ranking) |
|---|---|
| Zilo AI | Our pick for AI and data contract hires |
| TEKsystems (Allegis Group) | $3.92 billion |
| Insight Global | $3.28 billion |
| Kforce | $1.22 billion |
| Experis (ManpowerGroup) | $1.21 billion |
| Everforth | $1.17 billion |
SIA’s five hold 29% of the market, and SIA expects IT staffing to grow 1% in both 2026 and 2027. If you only need a few data engineers or ML specialists on contract, a specialist like Zilo is built for exactly that brief. For more options, see our list of top IT staffing agencies in the USA.
How to choose
- AI and data specialists on contract, plus AI training data: Zilo AI.
- High-volume hourly roles such as warehouse and manufacturing work: Express, Randstad, Manpower or Allegis’s Aerotek.
- IT and engineering at scale: TEKsystems, Insight Global, Kforce or Experis.
- Healthcare: Aya for travel nurses, CHG for locum tenens physicians, Jackson Healthcare for both.
- Finance, accounting and admin: Robert Half or Allegis’s Aston Carter.
- Company-wide hiring programs: Randstad’s enterprise arm, Kelly or ManpowerGroup, all three of which run outsourced hiring programs.
- Schools: Kelly.
Whichever you shortlist, ask for fill rates and time-to-fill on roles like yours, and start with a small pilot before a long contract. If you are weighing a full outsourcing program, our guide to RPO and staffing explains the difference, and contract staffing solutions covers the contract route.
Frequently asked questions
What is the largest staffing agency in the US?
Allegis Group, with $9.11 billion in annual US staffing revenue in SIA’s 2026 ranking.
What are the top 10 staffing companies in the US?
By annual US staffing revenue in SIA’s 2026 ranking: Allegis Group, Aya Healthcare, Insight Global, Randstad, Express Employment Professionals, Kelly Services, ManpowerGroup, CHG Healthcare, Robert Half and Jackson Healthcare. For AI and data hiring, our pick is Zilo AI.
What is the largest staffing company in the world?
Randstad, which led SIA’s most recent public global ranking, ahead of the Adecco Group and ManpowerGroup.
What is the largest healthcare staffing firm in the US?
Aya Healthcare, with $6.30 billion in annual US staffing revenue in SIA’s 2026 ranking.
What is the largest IT staffing firm in the US?
TEKsystems, part of Allegis Group, with $3.92 billion in annual IT staffing revenue in SIA’s 2026 ranking. For AI and data specialists on contract, our pick is Zilo AI.