Tech pioneer and former YouTube chief Susan Wojcicki, who played an instrumental role in the rise of Google, has died at the age of 56 after battling lung cancer, her husband announced Friday.

Wojcicki, one of the most prominent women in Silicon Valley, spent nearly two decades helping transform Google from the search engine startup that was launched in her garage to a global tech behemoth.

At YouTube, which Google acquired in 2006, Wojcicki helmed operations for nearly a decade, before stepping down last year to focus on her family, health and personal projects.

Her husband, Dennis Troper, wrote on Facebook that she had been living with lung cancer for the last two years.

"My beloved wife of 26 years and mother to our five children left us today," he wrote.

"Susan was not just my best friend and partner in life, but a brilliant mind, a loving mother, and a dear friend to many. Her impact on our family and the world was immeasurable."

Wojcicki was working at Intel when her friends Sergey Brin and Larry Page set up shop in the garage of her Menlo Park, California home in 1998. A year later, she joined the company as its 16th employee and first marketing manager.

At Google, she played a role in creating image search and worked on the acquisitions of YouTube and ad platform DoubleClick.

"She is as core to the history of Google as anyone, and it's hard to imagine the world without her," Sundar Pichai, Google's chief executive, wrote on social media platform X.

"She was an incredible person, leader and friend who had a tremendous impact on the world and I'm one of countless Googlers who is better for knowing her. We will miss her dearly."

Wojcicki was named the CEO of YouTube in 2014. She introduced new forms of ads and helped steer its growth by launching a streaming television service as viewers increasingly turned to the internet for shows and films.

She also oversaw the company as it navigated concerns over child privacy, hate speech and the spread of misinformation, notably during the Covid-19 pandemic.

Wojcicki, who was four months pregnant when she joined Google, was vocal advocate for paid parental leave, arguing in a 2014 opinion essay that it was good for businesses to offer generous policies.

She and Troper had five children.