Google+ (sometimes written as Google Plus, stylized as G+ or g+) was a social network owned and operated by Google until it ceased operations in 2019. The network was launched on June 28, 2011, in an attempt to challenge other social networks, linking other Google products like Google Drive, Blogger, Google AdSense, and YouTube. The service, Google's fourth foray into social networking, experienced strong growth in its initial years, although usage statistics varied, depending on how the service was defined. Three Google executives oversaw the service, which underwent substantial changes that led to a redesign in November 2015.

Due to low user engagement and disclosed software design flaws that potentially allowed outside developers access to personal information of its users, the Google+ developer API was discontinued on March 7, 2019, and Google+ was shut down for business and personal use on April 2, 2019.

Google+ was the company's fourth foray into social networking, following Google Buzz (introduced 2010, retired in 2011), Google Friend Connect (introduced 2008, retired in March 2012), and Orkut (introduced 2004, retired in September 2014).

Google+ was introduced in June 2011. Features included the ability to post photos and status updates to the stream or interest-based communities, group different types of relationships (rather than simply "friends") into Circles, a multi-person instant messaging, text and video chat called Hangouts, events, location tagging, and the ability to edit and upload photos to private cloud-based albums.

According to a 2016 book by a former Facebook employee, some leaders at Facebook saw Google's foray into social networking as a serious threat to the company. Facebook founder Mark Zuckerberg instituted a company-wide "lockdown", signaling that employees were supposed to dedicate time to bringing Facebook's features into line with Google+.

Assessments of Google+ growth varied widely, because Google first defined the service as a social network, then later as "a social layer across all of Google's services", allowing them to share a user's identity and interests. According to Ars Technica, Google+ signups were "often just an incidental byproduct of signing up for other Google services."

In 2011, Google+ had 10 million users two weeks after the launch. In a month, it had 25 million. In October 2011, the service had 40 million users, according to Larry Page. At the end of 2011, Google+ had 90 million users. In October 2013, approximately 540 million monthly active users used the social layer by interacting with Google+'s enhanced properties, such as Gmail, the +1 button, and YouTube comments. Some 300 million monthly active users participated in the social network by interacting with the Google+ social-networking stream. According to ComScore, the biggest market was the United States followed by India.

Google+'s user engagement was lower than that of its competitors; ComScore estimated that the average amount of time spent by users on the site during the month of January 2012 amounted to only 3.3 minutes, while on Facebook this metric was over 136 times greater, at 7.5 hours. In March 2013, average time spent on the site had increased but remained low, at about 7 minutes according to Nielsen (not including traffic from apps). In February 2014, The New York Times likened Google+ to a ghost town, citing Google's stated 540 million "monthly active users" and noting that almost half did not visit the site. The company replied that the significance of Google+ was less as a Facebook competitor than as a means of gathering and connecting user information from Google's various services.