When to arrive to Istanbul airport (IST)

This airport is vast, distances between things are loooong. There are multiple security screenings you have to go through (although IME they are all quick and efficient). This is not an airport you want to show up late to. I'd be there 3 hours ahead of scheduled departure (then again, I'd also be looking forward to spending an hour of that in the Turkish Airlines lounge...). You will have ample opportunity to stretch your legs.

At a minimum, 3 hours ahead of time. Lots and lots of security checks. Just to get into the airport you have to stand in line and go through a security checkpoint. And there is a lot of walking as I recall.

I'd also be looking forward to spending an hour of that in the Turkish Airlines lounge

Unfortunately Turkish Airlines doesn't offer paid access to their lounges so unless the OP is flying business or has elite status with the airline or Star Alliance they won't be able to use the lounges. The only paid option are the iGA lounges but they're not in the same league as the Turkish Airlines ones.

I'll also echo the sentiment to arrive early due to the size of the airport. When I last flew from there I arrived with three hours to spare and that was a comfortable buffer but I certainly wasn't left twiddling my thumbs. Next week I've given myself a 3 1/2 hour connection time but that is mainly so that I can make the most of the TA lounge.

Definitely three hours ahead, for all the reasons already provided. If you're staying in the historic center, it takes 45-60 minutes minimum to get to the airport by car or taxi. Depending on your flight departure time, you might consider staying at a hotel much nearer the airport the night before your flight.

Thank you for the advice on timing. And we do plan to take advantage of our Gold Star Alliance member lounge access! Thank you

I forgot to mention that we are staying in the beach town of Kumköy the night before (near Kilyos and not to be confused with the one). Our transfer service estimates a 25-30min trip to the airport.

Thank you for the advice on timing. And we do plan to take advantage of our Gold Star Alliance member lounge access!

Excellent! Enjoy, it's a very good lounge with great food and drink.

Try the lentil soup if they're serving it - it's excellent.

I was extremely excited to read your post. I too am flying from IST but to Paris on a 450am flight. Since it is about an hour from my apt in Istanbul I have a private car scheduled for 2am. I have 2 free United passes and with your post realized I am flying Turkish Air which is part of United's Star Alliance. I think my plan at this point might be to book a midnight car, get to the airport around 1am and since it is well within the 4 hours prior to a flight criteria, use the lounge. I plan on checking this out with United as my whole ticket is with Delta.

I am also bringing the luggage "sticker" that came with my carryon when I bought it to show that exact dimensions the manufacturer says to avoid any measurement issues. Enjoy your trip.