Three documentaries that constantly get recommended by vegans are: Earthings, Forks over Knives, and Cowspiracy. Between them they broadly cover the animal rights, health, and environmental issues respectively. Look further down the page for recommendations that cover all topics in one.
If you get through Earthings, Forks over Knives, and Cowspiracy, you will go vegan.
The Vegan Documentary Trio
If you don’t believe that what happens in Earthling is happening in Australia then you must watch Lucent.
The Australian “Earthlings“
If you are going to watch just one documentary about veganism, watch Vegucated because it broadly covers all the topics, and despite looking a bit dated, the arguments are as sound as ever.