The prince will stand trial before the Higher Regional Court, together with eight others. Federal prosecutors accuse them of having been members of or having supported a terrorist organisation. They include former members of the German armed forces and a former member of parliament for the Alternative for Germany (AfD) party.
They are accused of belonging to the "Reichsburger" network. So-called "Citizens of the Reich" believe that the modern German republic illegitimately replaced the German Reich that was founded in 1871 and continued under the Nazi regime until 1945. They reject the legitimacy of Germany's modern federal state and its laws.
The trial is the second of three mammoth trials surrounding the alleged coup attempt. A trial against alleged members of the group's military arm began in Stuttgart at the end of April. Other alleged members will stand trial in Munich from June 18.
The plot was uncovered during a large-scale anti-terror raid in December 2022.
According to the indictment, the group began planning and preparing for "Day X" - the date of the coup - starting in August 2021.
Specifically, an armed group was supposed to infiltrate the parliament building in Berlin to arrest German politicians and then install a new interim government with Reuss as head of state.
They were said to have accepted they might have to sacrifice their lives to achieve their goals.
According to the prosecutors, around 500,000 euros ($543,000) and a large arsenal of weapons were made available to the conspirators. Concrete preparations, such as the recruitment of military personnel, had also taken place.
The accused were united by a deep rejection of state institutions and the free democratic order, according to the federal prosecutor's office, which has described the group's ideology as "a conglomerate of conspiracy theories."
The alleged leaders of the plot, Prince Reuss and Rudiger von Pescatore, a former soldier who is said to have led the military arm of the group, are on trial in Frankfurt.
Reuss is a descendant of a noble family whose princely title carries no formal weight. Germany's monarchy was abolished more than a century ago.
The outlines of structures for a separate state order are said to have been worked out, with Prince Reuss acting as head of state. The former Berlin judge and former AfD lawmaker Birgit Malsack-Winkemann, who is also one of the Frankfurt defendants, was supposed to have been the equivalent of the justice minister.
Strict security precautions are in place for the trial. A lightweight metal hall with an area of around 1,300 square metres has been specially erected on the outskirts of Frankfurt.
According to the court, the defendants face up to 10 years in prison if they are found guilty on one charge. In the event of several guilty verdicts and a total sentence, they would face a maximum of 15 years in prison. The accused are presumed innocent until a judgment is reached.
In addition to the trial in Frankfurt, other members of the group in Stuttgart and Munich must also stand trial before the respective higher regional courts.
The trial in Frankfurt alone is of unprecedented dimensions for the Higher Regional Court, court spokeswoman Gundula Fehns-Boer said. The indictment comprises 617 pages.
Nine defendants, five judges, two supplementary judges and no fewer than 25 defence lawyers will be present at the trial. Ten people were originally scheduled to stand trial, but one of them died in a hospital in March, the court spokeswoman said.
Around 260 witnesses will be summoned, and 40 to 45 police officers will provide security to them on each day of the trial. The court has scheduled 48 trial days through January.