KataGo is a free and open-source computer Go program, capable of defeating top-level human players.

KataGo supports the Go Text Protocol, with various extensions,[5] thus making it compatible with popular GUIs such as Lizzie.

KataGo is widely used by strong human go players, including the South Korean national team, for training purposes.

[10] Based on techniques used by DeepMind's AlphaGo Zero, KataGo implements Monte Carlo tree search with a convolutional neural network providing position evaluation and policy guidance.

Compared to AlphaGo, KataGo introduces many refinements that enable it to learn faster and play more strongly.

While AlphaGo Zero has only game board history as input features (as it was designed as a general architecture for board games, subsequently becoming AlphaZero), the input to the network contains additional features designed by hand specifically for playing Go.

In 2022, KataGo was used as the target for adversarial attack research, designed to demonstrate the "surprising failure modes" of AI systems.