- I-CASE Integrated Computer-Assisted Software Engineering
- I-D Internet Draft
- I/G Individual/Group
- I/O Input/Output
- IAB Internet Architecture Board / Internet Activities Board
- IAC Interpret As Command / Inter-Application Communications
- IAFA Internet Anonymous ftp Archives
- IANA Internet Assigned Numbers Authority
- IANAD I Am Not A Doctor
- IANAL I Am Not A Lawyer
- IAP Internet Access Provider
- IBA Internet Business Association
- IBM International Business Machines
- IC Integrated Circuit
- ICE In-Circuit Emulator
- ICM Independent Color Matching
- ICMP Internet Control Message Protocol
- ICP Internet Control Protocol
- ICW Initialization Command Word
- IDAPI Independent Database Application Programming Interface
- IDE Integrated Drive Electronics / Integrated Development Environment
- IDEA International Data Encryption Algorithm
- IDI Initial Domain Indicator
- IDL Interface Definition Language
- IDMS Integrated Data Management System
- IDP Internetwork Datagram Protocol / Initial Domain Part
- IDT Interrupt Descriptor Table
- IE Interrupt Enable
- IEC International Electrotechnical Commission
- IEEE Institute of Electrical and Electronics Engineers
- IEN Internet Experiment Note
- IESG Internet Engineering Steering Group
- IETF Internet Engineering Task Force
- IFD Image File Directory
- IGES Initial Graphics Exchange Specification
- IGP Interior Gateway Protocol
- IGRP Interior Gateway Routing Protocol
- IGS Internet Go Server
- IINREN Interagency Interim National Research and Education Network
- IMCO In My Considered Opinion
- IMHO In My Humble Opinion
- IMNSHO In My Not-So-Humble Opinion
- IMO In My Opinion
- IMPS Interface Message ProcessorS
- IMR Internet Monthly Report
- IOC Inter-Office Channel
- IOW In Other Words
- IP Instruction Pointer / Internet Protocol
- IPC InterProcess Communication
- IPng Internet Protocol next generation
- IPUMS Integrated Public Use Microdata Series
- IPv6 Internet Protocol version 6
- IPX Internetwork Packet EXchange
- IR Internet Router
- IRC Internet Relay Chat
- IrDA Infrared Data Association
- IREQ Interrupt REQuest
- IRQ Interrupt ReQuest
- IRSG Internet Research Steering Group
- IRTF Internet Research Task Force
- IS Intermediate System
- IS-IS Intermediate System-to-Intermediate System Protocol
- ISA Industry Standard Architecture
- ISDN Integrated Services Digital Network
- ISI Information Sciences Institute
- ISIS Investigative Support Information System
- ISM Industrial Scientific and Medical
- ISO International Standards Organization
- ISO/OSI International Standards Organization/Open System Interconnection model
- ISOC Internet SOCiety
- ISODE International Standards Organization Development Environment
- ISP Internet Service Provider
- ISR Interrupt Service Routine
- ISV Independent Software Vendor
- ITL International Telecommunications Union
- ITT International Telephone and Telegraph
- ITU International Telecommunication Union
- IU Integer Units
- IVHS Intelligent Vehicle Highway System
- IWM Integrated Woz Machine
- IXC IntereXchange Carrier