| I&RS | Instrument And Range Safety  
| Military |
| IR(S) | Incidence Rate(S)
| Others |
| IRS | I Remain Standing
| Others |
| IRS | I Respect Someone
| Others |
| IRS | I Ride Slow
| Others |
| IRS | I'm Really Sexy
| Others |
| IRS | I'm Really Sweet
| Others |
| IRS | Identical, Related, or Similar
| Others |
| IRS | Identify, Reduce, and Schedule
| Others |
| IRS | Illini Racing Series
| Others |
| IRS | Illinois Reading Society
| Others |
| IRS | Im Really Sweet
| Others |
| IRS | Image Results and Security
| Others |
| IRS | Implicit Radiation Solver
| Others |
| IRs | Impreza Rs
| Others |
| IRS | Improving The Republican Summer
| Others |
| IRS | In Range Shooting
| Others |
| IRS | Incident Reporting System
| Others |
| IRS | Income Revenue Service
| Others |
| IRS | Increased Rotational Speed
| Others |
| IRS | Increasing Returns to Scale
| Others |
| IRS | Independent Rear Suspension
| Others |
| IRS | Independent RV Sellers
| Others |
| IRS | Indian Readership Survey
| Others |
| IRS | Indian Register of Shipping
| Company, Logistics, Database, Transport, Water Transport |
| IRS | Indian Remote Sensing
| Others |
| IRS | Indian Residential Schools
| Others |
| IRS | Indian Revenue Service
| Others |
| IRS | Individualised Research Study
| Others |
| IRS | Indoor Residual Spray
| Others |
| IRS | Indoor Residual Spraying
| Others |
| IRS | Inertial Reference System
| Others |
| IRS | Infernal Revenue Service
| Others |
| IRS | Inflatable Restraint System
| Others |
| IRS | Information and Reconnaissance Ship
| Others |
| IRS | Information And Referral Services
| Others |
| IRS | Information and Reporting Services
| Others |
| IRS | Information Reporting System
| Others |
| IRS | Information Retrieval Service
| Others |
| IRS | Information Retrieval System
| Others |
| IRS | Infra Red Sensor
| Others |
| IRS | Infrared Locking System
| Others |
| IRS | Infrared Signature
| Others |
| IRS | Infrared Spectroscopy
| Others |
| IRS | Inhibit Republican Speech
| Others |
| IRS | Initial Receive Sequence
| Others |
| IRS | Inmate Roommate Soulmate
| Others |
| IRS | Innovative Reflection Spotlight
| Others |
| IRS | Insensitive Ruthless Shysters
| Others |
| IRS | Inserted Rectally Service
| Others |
| IRS | Instant Recreational Satisfaction
| Others |
| IRS | Instant Refund Station
| Others |
| IRS | Instinctive Reaction To Struggle
| Others |
| IRS | Institute of Regional Studies
| Others |
| IRs | Institutional Representatives
| Others |
| IRS | Instructor Rating System
| Others |
| IRS | Insulin Receptor Stke
| Others |
| IRS | Insulin Receptor Substrate
| Others |
| IRS | Insulin Resistance Syndrome
| Others |
| IRS | Integrated Reception System
| Others |
| IRS | Integrated Restraint System
| Others |
| IRS | Intel Real Sense
| Others |
| IRS | Intelligent Radar Sensor
| Others |
| IRS | Intelligent Register System
| Others |
| IRS | Intelligent Responsible Students
| Others |
| IRS | Intelligent Road Studs
| Others |
| IRS | Inter-Domain Routing Security
| Others |
| IRS | Interchange Record Separator
| Others |
| IRS | Interchange Recors Separator
| Others |
| IRS | Interest Rate Swap
| Others |
| IRS | Interested Readers Society
| Others |
| IRS | Interested Readers' Society
| Others |
| IRS | Interesting Readers Society
| Others |
| IRS | Interesting Rural Scenery
| Others |
| IRS | Interface Requirements Specification
| Others |
| IRS | Internal Regulating Services
| Others |
| IRS | Internal Responsibility Syndrome
| Others |
| IRS | Internal Revenue Selfies
| Others |
| IRS | Internal Revenue Service
| Others |
| IRS | Internal Revenue Services
| Others |
| IRS | Internal the R Stands
| Others |
| IRS | International Reference Star
| Others |
| IRS | International Relations Society
| Others |
| IRS | International Relief Service
| Others |
| IRS | International Responsibility Seminar
| Others |
| IRS | International Retail Service
| Others |
| IRS | International Revange Service
| Others |
| IRS | International Revenue Service
| Others |
| IRS | International Reynard Society
| Others |
| IRS | International Riot Society
| Others |
| IRS | International Rod Society
| Others |
| IRS | International Rongdoing Society
| Others |
| IRS | Internet Racer's Supply
| Others |
| IRS | Internet Radio Station
| Others |
| IRS | Intimate Relations Schedule
| Others |
| IRS | Intrapulse Raman Scattering
| Others |
| IRS | Inventory and Resource System
| Others |
| IRS | inverse Raman scattering
| Others |
| IRS | Inverse Repeated Sequence
| Others |
| IRS | Investor Relations Society
| Others |
| IRS | Invisible RattleSnakes
| Others |
| IRS | Irate Raging Spouse
| Others |
| IRS | Iron Ring Stag
| Others |
| IRS | Irreverent Rodent Society
| Others |
| IRS | Irritable Rabbit Syndrome
| Others |
| IRS | Irritable Ricky Syndrome
| Others |
| IRS | Irwin R. Scheister, wrestler (real name: Lawrence Michael Rotunda)
| Others |
| IRS | Isolation Resistance Sanitation
| Others |
| IRS | It Really Stinks
| Others |
| IRS | It's Really Sexy
| Others |
| IRS | It's Really Stealing
| Others |
| IRS | Italian Rhythm Section
| Others |
| IRS | Kirsch Municipal Airport
| Others |
| IRS | Resource (WordPerfect)
| Others |