Top 10 Largest Architecture Firms in the World (2026)

Quick answer: The largest architecture firms in the world are led by Gensler, which tops Building Design’s 2026 WA100 with around 2,716 fee-earning architects, followed by HDR, AECOM and Japan’s Nikken Sekkei. Rankings measure architect headcount and architecture revenue, so the order shifts by the yardstick used.

The studios behind the world’s tallest towers, busiest airports and largest hospitals tend to be enormous operations in their own right. They employ thousands of architects, run offices on several continents, and win work across every building type. This ranked look at the largest architecture firms in the world sets out who leads the field in 2026, where each practice is based, and the work that made its name.

Figures below draw on two industry benchmarks: Building Design’s annual World Architecture 100 (WA100), which ranks practices by the number of fee-earning architects, and Architectural Record’s Top 300, which ranks US firms by architecture-specific revenue. Numbers reflect the latest available rankings and change year to year.

How the Largest Architecture Firms Are Ranked

There is no single scoreboard for firm size, and the answer depends on what you count. The WA100 measures pure architect headcount, which rewards large multidisciplinary studios and puts Gensler well ahead of the field. Architectural Record’s Top 300 instead ranks by architecture revenue, a lens that lifts design-focused practices with high fees per project. A third measure, geographic reach, counts the number of countries and offices a studio can staff at once.

These measures rarely agree. Engineering-led groups such as AECOM and Stantec employ tens of thousands of people in total, yet only a share of that workforce holds an architecture license, so their WA100 position sits below their overall company size. Design studios like Zaha Hadid Architects rank lower on headcount but carry creative influence far beyond their staff numbers.

The 10 Largest Architecture Firms in the World

The table below lists ten of the biggest practices from the 2026 WA100 survey, with headquarters and the work each studio is known for. Figures are approximate architect headcounts, not total staff, since these firms also employ engineers, planners and support teams.

Source: Building Design WA100 2026 survey, ranked by fee-earning architects.

1. Gensler

Gensler has been the world’s largest architecture practice for years, running more than 50 offices across the Americas, Europe, the Middle East and Asia. Its work spans workplace interiors, airports, stadiums and supertall towers, with the 632-metre Shanghai Tower among its best known projects. Architectural Record placed its 2025 architecture revenue at roughly 1.95 billion dollars, well clear of any rival.

2. HDR

Based in Omaha, HDR is an employee-owned firm built around healthcare, science and transport work. Its architects design hospitals, research laboratories and university buildings alongside a large engineering arm, which is why it ranks near the top of the WA100 on headcount. HDR is a steady presence on healthcare-specific rankings, where clinical planning experience carries real weight.

3. AECOM

AECOM is an engineering and infrastructure group with a global architecture and buildings arm. Its projects lean toward master planning, transport and large public works, from stadiums to airport terminals. Because the wider company employs tens of thousands of engineers and consultants, its registered architects represent only a slice of the total, yet that slice is large enough to place it third on the WA100.

4. Nikken Sekkei

Headquartered in Tokyo, Nikken Sekkei is Asia’s largest architecture firm and one of the oldest, tracing its roots to 1900. It pairs Japanese design traditions with heavy urban-planning expertise, and its portfolio includes the Tokyo Skytree and large mixed-use districts across Japan and Southeast Asia. Sustainability and disaster-resilient design feature strongly in its recent work.

5. Perkins&Will

Chicago-based Perkins&Will is a consistent leader in sustainable design, with a long record of LEED-certified buildings across healthcare, education and corporate work. The firm operates studios worldwide and often ranks among the top handful of US practices by architecture revenue, sitting behind only Gensler on several recent Architectural Record lists.

6. Aedas

Aedas, headquartered in Hong Kong, is one of the few firms of this scale rooted in Asia rather than North America or Europe. It specialises in high-density mixed-use towers, retail complexes and transport hubs across China, the Gulf and Southeast Asia. Its regional focus gives it deep familiarity with fast-moving, large-plot developments in growth cities.

7. Foster + Partners

Foster + Partners is the most decorated studio on this list, founded by Pritzker laureate Norman Foster. Its buildings include Apple Park, London’s Gherkin and Bloomberg’s European headquarters, and the practice is known for low-energy engineering integrated into landmark design. It runs a smaller architect headcount than the US giants but competes at the very top on reputation and airport and tower work.

8. Stantec

Stantec, based in Edmonton, is a large Canadian design and engineering group whose buildings arm handles education, healthcare and community projects across North America and beyond. Like AECOM, its architecture team forms one part of a much broader consultancy, and repeated acquisitions have widened both its reach and its project range.

9. HOK

HOK, headquartered in St. Louis, is a long-established US practice with strengths in aviation, sports and healthcare. It has designed major airport terminals and stadiums worldwide, and its research into workplace and science buildings keeps it visible on sector rankings. HOK balances a broad building portfolio with a steady architect headcount rather than chasing raw scale.

10. Zaha Hadid Architects

Zaha Hadid Architects rounds out the list as the clearest example of influence outstripping size. The London studio ranks well below the headcount leaders, yet its fluid, parametric buildings, from the Heydar Aliyev Center in Baku to the Beijing Daxing Airport terminal, shape how the profession thinks about form. It shows that a place among the largest firms is only one measure of standing in architecture.

What Firm Size Tells You, and What It Does Not

Scale brings clear advantages. Large firms can staff several major projects at once, absorb the cost of research into materials and building performance, and open local offices to meet clients on the ground. That capacity is why global towers, airports and hospitals so often list one of these names as architect of record. For a wider view of reputation rather than raw size, see our look at the best architecture firms.

Size also has limits. Sector expertise, design quality and local knowledge matter more than headcount on most commissions, which is why specialists win work against far larger rivals. A hospital client is better served by a firm with a deep clinical record than by whichever practice happens to sit highest on the WA100, as our guide to healthcare architecture firms shows. Technology reshapes this balance too, and the way the BIM industry is changing practice lets smaller studios deliver complex work once reserved for the giants.

The Bigger Picture

The most telling detail in any ranking of the largest architecture firms is how little the different lists agree with each other. A studio can lead on headcount, trail on revenue and still define a decade of design through a handful of buildings. Size opens doors, but the practices people remember are the ones that did something with the space behind them.