Update (November 29, 2012): The poll is now closed. Stay tuned for results and reactions in the coming days…

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What’s does it mean to be the greatest? We’re being loose with the term… One might argue that the greatest documentary was the first (that might be Nanook of the North if you’re talking about feature-length films as we think of them today), or the one that the most people have paid to see (that might be Fahrenheit 9/11), or it might be the one that has won over so many critics that we might as well call it a day (Hoop Dreams).

But which film would you say is the most influential on the form? Which one best defines everything a documentary should do? Which one do you love watching over and over and over again?

When we set out to find the “greatest” documentary of all time, we knew it would be a challenge no matter how we approached it. But it’s been a while since anyone has asked film fans to help find the greatest documentaries, so POV is picking up the mantle! We’re taking inspiration from the list generated every ten years by Sight & Sound magazine, mixed in with some “American Idol”-style judging and the power of social media.

So, here’s your chance to make the case for which documentary is the “greatest.” Search for a documentary in the list above, or add one that’s missing, then give it a “thumbs up” to start pushing it in the right direction. The ranking system gives late additions a fighting chance — and don’t forget you’ve got social media by your side as well, so share your choices!

The poll closes on Thursday, November 29, 2012, at 5 PM Eastern, so vote early!