"I have some important news to share, and I wanted you to hear it from me: Today, I am announcing my intention to run for re-election to the United States Senate in 2018," Sanders wrote in a Twitter post.
The senator from the US state of Vermont pledged he would continue to be the fiercest opponent in the Senate to congressional Republicans and President Donald Trump.
Twitter users have split into two camps, with some of them opposed to the re-election of the US senator, while a great number are in favor.
Social media users have supported the idea of the US senator's re-election.
The US Senator was a contender for the Democratic presidential nomination but lost to Hillary Clinton.
Sanders has been representing Vermont in the US Senate since 2007.