Scott Banister is an entrepreneur, startup founder, and angel investor. He cofounded the anti-spam company IronPort, and he was an early advisor and board member at PayPal. He invented paid search advertising via keyword auction, a core business model for internet advertising companies.

He was an early investor in Powerset, a startup building a natural language search engine. His other private equity investments include Zappos, Topsy, Upstart, Affirm, Thumbtack, Postmates, Uber, Diamond Foundry, Flexport, Niantic, Fivetran, Turing, Magic, DuckDuckGo, Nervana Cloud, Crusoe Cloud, and TogetherAI. Banister also cofounded Zivity, an adult-themed social networking site, with his wife, Cyan Banister.

David Gelles has identified Banister as one of the PayPal Mafia, former board members of PayPal, influential investors in "a collection of some of the most valuable technology start-ups ever seen". He invested in PayPal's earliest version, and he served as a founding board member. In a 2019 VentureBeat article, Andrew Ganato and Scy Yoon wrote that Peter Thiel and Scott Banister had been the most prolific investors, each responsible for investing in more than 100 companies.