He's been nominated four times, but this year lost to Matthew McConaughey.
So the internet, of course, exploded with emotions.
It was a sad, sad moment.
In fact, "Poor Leo" was even trending on Twitter.
Some people joked about what Leo was really saying and thinking.
While others joked about his misfortune :(
Others used his films to express their sorrow.
And the internet basically imploded with "Poor Leo" moments.
Others made valid points.
Or likened it to losing a computer game.
But mostly people were just sad. Very, very sad.
But let's all stay positive.