The first presidential debate between Democratic nominee Hillary Clinton and Republican nominee Donald Trump starts at 8 p.m. CST. It will be on all the major broadcast networks (so CBS, NBC, Fox, ABC), as well as C-SPAN and pretty much all the cable news outlets.
But naturally it's also being streamed live online. There's a YouTube link up top for the Washington Post's feed. If it doesn't work for some reason, you can also try the NBC, Fox News and Bloomberg feeds. And Twitter has its own stream here.