What is the limit to number of Mystical Space Typhoons you can have in a deck Yu-Gi-Oh cards?

You can only have 3 copies of Mystical Space Typhoon in a single Yu-Gi-Oh! deck.

This is the standard limit for any single card in a deck, with a few exceptions. The exceptions include:

* Some cards have a specific limit. For example, some cards have a limit of 1, such as "Pot of Greed."

* Some cards are banned or limited in certain formats. These cards are not allowed in any deck or have a limited number of copies allowed.

Therefore, you can have a maximum of 3 Mystical Space Typhoons in your deck.