- I bear a charmed life
- I have not slept one wink
- I have nothing to declare but my genius
- I have nothing to offer but blood toil tears and sweat
- I haven't got a clue
- I see no ships
- I see you stand like greyhounds in the slips
- I spy with my little eye
- I told you is was ill
- I will swing for you
- I will wear my heart upon my sleeve
- Identity theft
- Idioms quiz
- the Ides of March
- If I had my druthers
- If it ain't broke, don't fix it
- If music be the food of love, play on
- If the cap fits
- If the mountain will not come to Muhammad, then Muhammad must go to the mountain
- If the shoe fits
- If wishes were horses, beggars would ride
- If you can't stand the heat, get out of the kitchen
- If you lie down with dogs, you will get up with fleas
- If you think that, you have another think coming
- Ill wind
- I'll be there with bells on
- I'll go to the foot of our stairs
- I'll have your guts for garters
- I'm stumped
- Imitation is the sincerest form of flattery
- In a blue funk
- In a cleft stick
- In a pickle
- In a pig's eye
- In a quandary
- In a nutshell
- In a trice
- In an interesting condition
- In for a penny, in for a pound
- In like Flynn
- In limbo
- In my minds eye
- In someone's bad books
- In spades
- In stitches
- In the bag
- In the box-seat
- In the buff
- In the cart
- In the catbird seat
- In the club
- In the doghouse
- In the doldrums
- In the limelight
- In the nick of time
- In the pink
- In the red
- In the same boat
- In the sticks
- In your face
- Including, but not limited to
- Indian giver
- Indian summer
- Infra dig
- Innocent until proven guilty
- Inside out
- intents and purposes
- Iron hoof
- Is the Pope Catholic?
- Is the Pope Polish?
- Is this a dagger which I see before me?
- It ain't over till the fat lady sings
- It came like a bolt from the blue
- It is meat and drink to me
- It never rains but it pours
- It's all Greek to me
- It's all grist to the mill
- It's better to give than to receive
- It's better to have loved and lost than never to have loved at all
- It's better to light a candle than curse the darkness
- It's not rocket science
- It's that man again
- Itty-bitty
- Ivory tower