Ahmad Ali Abdelkader, 31, was charged with "insulting state institutions and symbols" and "negatively speaking about the kingdom's policies", HRW said in a statement Tuesday.
It added the charges were related to tweets and interviews in which he expressed support for Sudan's 2018-2019 revolution -- and criticised Saudi's actions in his home country and Yemen.
"Jailing a media personality on bogus charges speaks more negatively about Saudi Arabia's policies than anything Ahmad Ali Abdelkader ever posted," said Michael Page, HRW's deputy Middle East director.
"This and other similar prosecutions demonstrate just how determined Saudi authorities are to stamp out even the most minor criticism or questioning on social media and deter all dissent under threat of long prison sentences."
According to HRW, Abdelkader was arrested at Jeddah airport on April 19 and denied access to a lawyer during the trial.
He was held for 20 days at a police station in Jeddah and then transferred to Al-Shumaisi detention centre near Mecca before facing a judge, they added.
The trial consisted of two short sessions, where he was unable to defend himself, said HRW, citing a source with direct knowledge of the case.
The source added that Abdelkader was interrogated twice during his detention and accused of behaviour on Twitter that was harmful to the kingdom.
Abdelkader worked in Saudi Arabia for five years between 2015 and 2020 but travelled back to the kingdom in April on a new work visa and was arrested upon entry.
"Saudi Arabia's Jeddah criminal court sentenced him on the basis of tweets and statements made to the media during and after February 2018, most of which he posted while based in Saudi Arabia, as well as email exchanges he had with major international human rights organisations in which he inquired about membership and subscribed and received newsletters," HRW said in the statement.
"Human Rights Watch reviewed the nine tweets and two media interviews explicitly mentioned in the court ruling and determined that none of them incited violence, hatred, or discrimination."
