IRR may refer to:
- Internal rate of return, a profitability metric
- Image rejection ratio, a radio metric
- Implied repo rate, a rate of return attained by means of a cash and carry trade
- Internet Routing Registry, a network routing database
- Iranian rial, the currency of Iran
- Individual Ready Reserve, a personnel status of the United States Military
- Iraqi Republic Railways, a transportation operator
- Institute of Race Relations, a policy institute
- Incident Response Regiment (Australia), an emergency response agency
- Institute for Religious Research, an apologetics organization
- Inner Ring Road (disambiguation)
- Interrupt Request Register, a register used for managing interrupts in programmable interrupt controllers.