The two activists used climbing equipment to climb the bridge and attach a banner, which in turn led to the bridge having to be shut down for almost 24 hours last fall. The action led to major traffic jams.
Southend Crown Court sentenced one of the two defendants to three years in prison, and two years and seven months in prison to the other.
“You are being punished for the chaos you caused and to discourage others from doing the same,” said the judge.
The two convicts belong to the Just stop oil group. They have been in custody since October 20, when the protest was carried out.
Around 160,000 vehicles cross the Queen Elizabeth II Bridge daily.