| Ideology | Principles, Convictions, Tenets, Philosophy |
| Illogical | Incongruent, Rambling |
| Illusory | Illusive, Imaginary, Fictional, Unreal |
| Illustrious | Distinguished, Famous, Noted, Renowned, Famed |
| Immaculate | Spotless, Unblemished, Pure, Clean |
| Immense | Enormous, Gigantic, Extensive, Vast, Huge, Massive |
| Imminent | Impending, Looming, Threatening, Menacing |
| Impartial | Candid, Impersonal |
| Impair | Weaken, Cripple, Damage, Harm, Mar, Injure |
| Impassive | Cool, Apathetic, Calm, Serene, Composed, Unmoved |
| Impeach | Charge, Accuse, Arraign, Indict, Incriminate, Implicate |
| Imperative | Mandatory, Necessary, Requisite |
| Imperceptible | Undetectable, Invisible, Indiscernible, Indistinguishable, Obscure |
| Impertinence | Insolence, Boldness, Brazenness, Impudence, Presumption |
| Implicate | Involve, Include, Associate, Embroil |
| Importune | Beg, Solicit |
| Implicit | Implied, Indirect, Inferable, Understood, Unspoken |
| Impudent | Shameless, Impertinent, Insolent, Disrespectful, Forward |
| Inadvertent | Accidental, Unintentional, Unthinking |
| Incapacitate | Disable, Cripple, Paralyze, Wounded, Maim |
| Incongruous | Inconsistent, Inharmonious, Disharmonious, Discordant |
| Indigent | Needy, Poor, Destitute |
| Indolence | Laziness, Slothfulness, Sloth, Sluggishness, Idleness |
| Ingenious | Clever, Skilled, Shrewd, Cunning |
| Ingenuous | Naive, Simple, Innocent, Unsophisticated |