Neural Networks: Zero to Hero

Andrej Karpathy's Neural Networks: Zero to Hero is a free video series teaching neural networks from first principles. You implement neural networks from scratch in Python, no frameworks, so you understand exactly how they work. The course is advanced but exceptionally clear. After finishing, you understand backpropagation, gradient descent, and how to build neural networks. Karpathy is Tesla's former AI director and one of the best ML educators. The main limitation: this is math-heavy and requires linear algebra and calculus comfort.

Andrej Karpathy is a legendary AI researcher and educator, and his Zero to Hero series has become one of the gold standards for learning deep learning (source: community feedback).