Regulation S (Reg S) is the SEC exemption from US securities registration for offers and sales made outside the United States to non-US persons. It is distinct from Regulation D (which covers domestic offerings to US accredited investors), allowing US companies to raise capital from international investors without registering the offering with the SEC under the Securities Act of 1933. It is the regulatory mechanism most commonly used when US startups raise from sovereign wealth funds, foreign family offices, foreign corporations, or other non-US investor types.
The two main "safe harbors" within Reg S: