Here are leading corporate / managed-travel agencies active across the Middle East (short description + source for each):

• dnata Travel (dnata Travel Management) — major UAE-headquartered corporate travel manager and one of the region’s largest TMCs; partner to Amex GBT for regional delivery. (mediaoffice.ae)
• FCM Travel Solutions (Flight Centre Travel Group) — large regional TMC with UAE hub and MENA coverage; multiple industry awards for Middle East TMC. (fcmtravel.com)
• American Express Global Business Travel (Amex GBT) — global TMC with a strong Middle East presence (including joint ventures/partnerships with regional groups). (zawya.com)
• BCD Travel — global corporate travel company with established UAE operations and local executive team in Dubai. (bcdtravel.com)
• CWT (Carlson Wagonlit Travel) — international TMC operating in the Gulf via local partners (e.g., Orient Travel / Alshamel) to service corporate clients in UAE and wider region. (mycwt.com)
• Kanoo Travel / Kanoo-GBT partnership — longstanding regional travel network (Kanoo) working with global TMCs to serve GCC markets. (zawya.com)
• Musafir and other regional digital/OTA groups — Dubai-based Musafir is an example of a large regional online travel agency that also supports corporate/leisure bookings across the GCC. (en.wikipedia.org)

Notes:

• Many global TMCs serve the Middle East via local partners, joint ventures or regional hubs (so the “provider” for a corporate programme is often a mix of a global brand plus a local partner). (zawya.com)
• If you want a ranked shortlist for RFPs (by market share, corporate volume, technology, 24/7 support, MICE capability, or by country — e.g., UAE vs Saudi Arabia vs Qatar) I can produce a tailored shortlist and suggested selection criteria; say which metric matters most and I’ll include recent market references.