The influence of the Stanford University computer scientist Rajeev Motwani, who has been found dead in the swimming pool of his California home, at the age of 47, stretched beyond Silicon Valley to affect the lives of millions of people around the world.

Known among his peers as having a brilliant mind, Motwani was an award-winning professor whose work in data mining and algorithms scooped a string of accolades, including the prestigious Gödel prize (2001). But it was in his role as a mentor and adviser to some of the world's most powerful technology companies - including his pivotal part in the development of the internet search engine Google - that he made the greatest impact. He had a critical role in assisting the graduate research of the Google founders Sergey Brin and Larry Page, encouraging the duo and helping them develop the systems that made them billionaires, so kickstarting what has probably become the pre-eminent company of the 21st century.

Like many of America's pioneering technologists, Motwani was an immigrant, born in the Indian border city of Jammu to a military family. With his father in the army, the family moved regularly, but the young Rajeev was soon sent to the St Columba's boys' school in New Delhi. He showed an aptitude for numbers at an early age, and soon expressed a desire to become a mathematician, inspired partly by the family's collection of biographies of famous scientists, including his hero, the 19th-century German genius Carl Gauss.

When the time came to consider university, however, Motwani's family encouraged him to study computer science, which was a sideways move that they saw as more stable and lucrative than pure mathematics. Despite his protestations, Motwani enrolled at the Indian Institute of Technology in Kanpur and swiftly discovered that computer science was, after all, a highly mathematical discipline.

By the time he graduated in 1983, the home-computer explosion was in full swing, and he moved continents to conduct research for a PhD (1988) at the University of California, Berkeley. Within a few years he became a professor at Stanford, the institution that spawned companies including Hewlett- Packard, Cisco and Sun Microsystems and has a unique role at the heart of California's hi-tech industry.

Thus Motwani was at the academic summit of technology, and over the years oversaw the work of many students as director of graduate studies in the computer science department, and became involved in fields such as robotics, data manipulation and even drug design. However, his most profound impact came when he played a role in guiding the work of Brin and Page. As an expert on data mining and algorithms, Motwani saw an incredible opportunity in the worldwide web, and helped start a number of classes and groups at Stanford aimed at investigating how to apply the mathematical principles he had worked on to the online world.

When approached by Brin for advice, he was initially sceptical that a new web search engine could make a difference in a crowded market. However, he saw something different in their work and co-authored several papers that developed their strategy for finding information online - taking on the role of informal adviser to Google as a result. In return for his involvement, Motwani was rewarded with a stake in the company, a relationship that paid off when Google reached the stockmarket in 2004, making Page and Brin billionaires and reaping great rewards for himself.

Although Motwani did not get the mainstream recognition that his former students achieved, the experience turned him even further towards helping nascent technologists and he found entrepreneurial zest intoxicating. As an adviser and investor to a string of other companies, including the internet payments service PayPal and venture capital firm Sequoia Capital, he quickly became one of the best-connected figures behind the scenes in Silicon Valley.

Motwani gained a reputation for never turning away a question and going out of his way to help any entrepreneur who asked him for advice. Confident but not brash, unlike many of his peers, he was described by his friend Ron Conway, another technology investor, as "one of the smartest people who has ever existed in Silicon Valley". By the time he was interviewed by Business India in 2007, Motwani had a different way to describe himself: a "startup junkie".

He is survived by his wife, Asha Jadeja, and daughters Naitri and Anya.

• Rajeev Motwani, computer scientist, born 26 March 1962; died 5 June 2009