Amnesty International says Ibrahim Halawa is innocent of all charges and is calling for his immediate release from an Egyptian prison.
Today is his 19th Birthday and a candlelight vigil is taking place outside the Egyptian Embassy in Dublin at 4pm.
He is been held in an Egyptian prison for 463 days without trial, after being arrested following the overthrow of President Mohamed Morsi.
His three sisters, who were arrested at the same time, were allowed to come back to Ireland.
A mass trial involving Ibrahim and hundreds of others is due to start next month.
Amnesty International Ireland's Colm O'Gorman says it is a travesty of justice.
"Ibrahim is due to stand trial with around 400 other people," he said.
"Very often, the death sentence is applied en masse to people who are subject to these trials, defence lawyers are very often not heard, very often defendants are not even in court, and no evidence in heard on behalf of the defendant in these trials.
"That's why we believe them to be a travesty of justice, and they bear none of the standards of fair trial processes."