Making the announcement via a posting on his own Google+ page on Thursday, Gundotra, 45, said he was proud of his eight year tenure with the online search giant, but felt that now was the time to look ahead. However, he didn't say much about his future plans.
"I am excited about what's next. But this isn't the day to talk about that. This is a day to celebrate the past 8 years," wrote Gundotra, who was Senior Vice-President, Social for Google in a post titled, "And Then."
"I'm also forever in debt to the Google+ team. This is a group of people who built social at Google against the scepticism of so many."
His departure follows a rumour posted two days ago on the app Secret that, "Vic Gundotra is interviewing," according to technology site CNet.
Citing a person familiar with the matter, it said that Gundotra had problems with Google's management team.
CEO Larry Page praised Gundotra in his own Google+ post, thanking him for "a tremendous almost eight years at Google" and for building Google+ "from nothing."
"I really enjoy using Google+ on a daily basis, especially the auto awesome movies which I really love sharing with my family and friends," said Page.
In addition to spearheading the development of Google+, Page congratulated Gundotra for his work on guiding the teams that introduced turn-by-turn navigation to Google Maps, and improving Google's developer relations, which Page described as "disparate efforts" before Gundotra fixed them.
However, his tenure was also a rocky one, according to CNET. Soon after the launch of Google+, Gundotra came under heavy criticism for insisting that Google+ users must display their real names, as opposed to pseudonyms.
Gundotra came to Google in 2007, following a 16-year stint at Microsoft as a general manager and a year off working on charitable causes.
Gundotra has not revealed where he will be going, although his abrupt departure indicates that he could be going to a competitor, CNET said.
The future of the social network that Gundotra founded is almost as unclear as Gundotra's next move, it said.
Going forward, Google+ will not be led by Gundotra's right-hand man and the social network's product manager Bradley Horowitz, reported Recode.
Instead, Google confirmed that Google+ Vice President of Engineering David Besbris will take command of Google+.
What Besbris' plans for Google+ are as-yet unknown, CNET said. There's been a lot of speculation that popular Google+ services like Photos will be broken off and the social network will be re-purposed as a platform.
However, Google "vehemently" denied the rumours to CNET.
"Today's news has no impact on our Google+ strategy-we have an incredibly talented team that will continue to build great user experiences across Google+, Hangouts and Photos," a Google representative was quoted as saying.
Google+ was launched in 2011 as Google's first foray into the expanding sector of social media, and was meant to compete head-on with leaders Facebook and Twitter.
As of last year, Google+ had 540 million active users, putting it ahead of Twitter's user base around the time but only about half of the over 1.2 billion active Facebook users around the world.