What is the total supply limit of Bitcoin?

The total supply limit of Bitcoin is 21 million bitcoins (BTC). This limit is hardcoded into the Bitcoin protocol and is designed to be a deflationary mechanism. The issuance of new bitcoins is halved approximately every four years through a process called "halving," which reduces the rate at which new coins are introduced into circulation until the maximum supply of 21 million bitcoins is reached. This limit is expected to be reached around the year 2140.