This thesis focuses on kidnapping in Colombia conducted by Illegal Armed Groups and investigates whether or not these kidnappings constitutes a crime against humanity according to article 7 of the Rome Statute for the International Criminal Court. My approach involve arguments for and against such categorization and investigate related sub questions, such as: How well this crime fits categories listed in article 7 of the Rome Statute? Could the effect of this crime on society be so severe that it should be considered an international crime and consequently a crime against humanity? Can kidnapping be in violation of international customary law? This thesis shows that kidnapping perpetrated by Illegal Armed Groups fits the required elements of crimes against humanity of article 7 of the Rome Statute in the categories 7 (1) (e) and 7 (1) (k) and it also constitute a violation of international customary law. The thesis concluded that kidnapping perpetrated by Illegal Armed Groups in Colombia should be considered a crime against humanity.