For stays of 90 days or less, nationals of 38 countries on the ESTA Visa Waiver Program (VWP) list are not required to get a visa before visiting the United States for leisure or business.
Instead of requesting a visa at a U.S. consulate, the VWP enables qualified tourists to request admission to the country at the point of entry.

As of 2021, the VWP ESTA countries are: Andorra, Australia, Austria, Belgium, Brunei, Chile, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, the Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, Taiwan, United Kingdom.

It’s important to note that the U.S. government has the power to choose which nations are included in the VWP and can exclude or add nations based on security considerations.
It is advised to confirm the most recent list before making travel arrangements to the US as this list of VWP nations is subject to change over time.