Yes, but you can buy a visa at the airport when you arrive. It's good for 3 months and costs $20, payable in dollars or euro.
If you are landing at Ataturk Airport in Istanbul, follow the crowds to the passport control. Before you get in line to passport control, you will see a set of windows on the left. This is where they sell visas. There will be a list of countries with the cost and length of validity for visas. They will take your cash, pop a sticker in your passport, and then you can line up to go through passport control.
