I want to use events that happened in a documentary in my novel. Is this legal? Do I have to contact them and request permission?

I am not sure what you mean by "events that happened in a documentary". You could mean: 1) historical events that were revealed in a documentary (eg, in Lincoln, the 15 Amendment was passed in Congress); 2) story telling in the documentary (eg, most of Daniel Day Lewis's lines were not actual quotes, but the creative work of the screenwriters); or 3) making of the documentary information (eg, how Daniel Day Lewis prepared to play President Lincoln). I'll do my best to hit all 3. 1. Facts are facts and cannot be copyright protected or otherwise possessed as someone's IP in the US (famous speeches can be copyright protected). If a documentary revealed a fact, you can use that fact in your own work, but you should endeavor to avoid using any creative elements sewn about the fact by the documentary producers. 2. Even documentaries have creative, artistic elements. These elements are protected just as strongly as they would be in a fictional work. It may not be legal to copy a creative event within a documentary (I say 'may' because a definitive answer would require clearer facts). The best way to confirm something is a fact is show that you came by the information from two independent sources. 3. Now we're getting back into facts and you can use facts without permission. Depending on the facts you use, you do want to make sure your source is solid and your recounting is accurate to avoid libel. Good luck, Todd