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9,937 companies in Oak Brook, Illinois.
Find 9,937 companies in Oak Brook, Illinois. From manufacturers to industrial suppliers, each listing carries the firm's address, website, size, and NAICS/SIC codes. You can also browse nearby cities such as Chicago, Naperville, Rockford.
Oak Brook, Illinois companies by size and revenue
| Employees | Companies | Share |
|---|---|---|
| 1-50 | 9,440 | 95.8% |
| 51-200 | 264 | 2.7% |
| 201-1000 | 123 | 1.2% |
| 1001-5000 | 22 | 0.2% |
| 5001+ | 9 | 0.1% |
| Revenue | Companies | Share |
|---|---|---|
| Under $10M | 9,219 | 95.9% |
| $10M-$50M | 268 | 2.8% |
| $50M-$250M | 91 | 0.9% |
| $250M-$1B | 24 | 0.2% |
| $1B+ | 12 | 0.1% |
Share is of companies with a known value — 9,858 with headcount and 9,614 with revenue on file, as of Jul 17, 2026.
Frequently asked questions
How many companies are in Oak Brook, Illinois?
9,937 companies in the directory are located in Oak Brook, Illinois.
How many large companies are in Oak Brook, Illinois?
73 of the 9,937 companies in Oak Brook, Illinois employ more than 500 people, and 12 report over $1 billion in annual revenue. See the size and revenue breakdown above for the full distribution.
What size are most Oak Brook, Illinois companies?
Most are small and mid-sized businesses: the size and revenue tables above show the full spread, from under $10M up to $1B+, across the 9,614 companies with revenue on file.
What information is included for each company?
Every listing includes the company name, location, website, employee size, revenue range where available, and NAICS/SIC classification, with a link to the full profile.
Where does this directory come from?
Listings are compiled and maintained by Factur, a sales and marketing firm for B2B manufacturers. Any company can request an update or removal from its profile page.