Human rights lawyers have filed the first cases against Syrian President Bashar al-Assad at the International Criminal Court (ICC) in The Hague.
The lawsuits were submitted on behalf of 28 Syrian refugees in Jordan who say they were forced to flee the country.
The legal teams are calling on the ICC to investigate possible crimes against humanity committed since Syria's civil war began in 2011.
The conflict has left more than 360,000 people dead and millions displaced.
Syria is not a party to the Rome Statute, the treaty that established the ICC, meaning that it has not been possible to bring an international criminal case against its government.
But lawyers have used a precedent set by a recent ICC ruling on Rohingya refugees in Bangladesh to launch two lawsuits this week.
In September, judges ruled that while Myanmar is not a member of the court, Bangladesh is, and that because part of the alleged crime happened on Bangladeshi territory the prosecutor does have jurisdiction.
The latest lawsuits have been filed based on this same principle, because Jordan - where the refugees fled - does fall under the ICC's jurisdiction.
Testimony from the refugees - in which they describe being shot at, bombed, and tortured - forms a substantial part of the evidence that has been submitted.
The first case was filed on Monday by the Guernica Centre for International Justice and the second was filed on Thursday by a team of British lawyers.
Rodney Dixon QC, who is leading the legal team that filed Thursday's lawsuit, said the case represented "a genuine breakthrough for the Syrian victims".
"There is a jurisdictional gateway that has opened up finally for the ICC prosecutor to investigate the perpetrators who are most responsible," Mr Dixon said in a statement.
Previous attempts to prosecute President Assad and members of his government have failed because the ICC has not accepted it has jurisdiction over Syria. There have also been cases where leaders charged by the ICC have managed to evade arrest.
Sudanese President Omar al-Bashir has successfully evaded arrest for several years despite facing charges of genocide, war crimes and crimes against humanity.