Randomized Algorithms – How to Generate a Random Rotation Matrix?

Is there a library or open source software that I can use to generate a random rotation matrix? If not, what is the best algorithm, the best theory, or the best method I can implement myself?

Actually, I do not know what "Random Rotation Matrix" really means, so I think the answer can come from the definition itself.

By the way, I have to create a high dimension of the "Random Rotation Matrix".

Ps. I've posted a question about this in Math Stack Exchange, link to the question. But I need more answers from the perspective of computer science.