- ICAT Expo
- ICG Communications
- ICMA
- Icon Health and Fitness, Inc.
- Iconographic Designs
- Idaho County
- Idaho County District Court
- Idaho State University
- Ideal Software, Inc.
- Ideal Steel and Builders Supply, Inc.
- IEPMPG - International Entertainment Production and Meeting Presentation Group
- IFMC-Encompass
- IG Sun Financial Services, Inc
- iGate Corporation
- Ignite Resources Center
- IHC
- IIAM
- IKM Inc.
- Ikon Office Solutions
- Illini Community Hospital
- Illinois Association of Community Action Agencies
- Illinois Association of School Boards
- Illinois Association of School Business Officials
- Illinois College
- Illinois Council of Health System Pharmacists
- Illinois Department of Public Health
- Illinois Health and Hospital Association
- Illinois Health Education Consortium-AHEC
- Illinois Institute of Technology Student Health and Wellness Center
- Illinois Manufacturers Association
- Illinois Secretary of State Organ-Tissue Donor Program
- Illinois Society of Association Executives
- Illinois State University
- Illinois Wesleyan University
- ILPP
- IMA
- Images Plus
- Imaging Concepts of NM
- IMC Global
- IMI Cornelius Inc.
- Immanuel Residences
- Immersion Medical
- Immigrant Resettlement and Cultural Center, Inc.
- IMN Solutions
- Impact America Media
- Impact Imaging
- Impact Solutions, Inc.
- Impella
- Imperial Construction Group, Inc.
- Imperial County