After US markets closed on Friday, Alphabet replaced Google as the publicly traded company that will house Google's search and Web advertising businesses, maps, YouTube and its "moonshot" ventures such as driverless cars.
Google's class A shares and class C shares will automatically convert into the same number of Alphabet class A shares and class C shares and start trading on the Nasdaq from Monday. The ticker symbols will not change.
The structural overhaul, announced in August, is intended to separate the company's core businesses from ventures such as the driverless cars, glucose-monitoring contact lenses and Internet-connected high-altitude balloons.
Google's Sidewalk Labs, a company dedicated to coming up with technologies to improve urban city infrastructure such as a free Wi-Fi programme, will also be a part of the Alphabet business.
The core businesses will be called Google and operate as a wholly-owned subsidiary of Alphabet. Sundar Pichai will head Google.
Alphabet will be run by Google co-founder Larry Page and each of its businesses will have its own chief executive.
Starting from the company's fourth quarter in January, Alphabet will have two reporting units - Google and all other Alphabet businesses taken as a whole.
Investors have cheered the move, saying it will give them greater visibility into the financial performance of Google's highly profitable core businesses.
Alphabet's businesses will also include connected home products maker Nest, venture capital arm Google Ventures, and Google Capital, which invests in larger tech companies.