The Internal Revolutionary Organisation (IRO; Bulgarian: Вътрешна Революционна Организация (ВРО), romanized: Vătrešna Revoljucionna Organizacija (VRO)) was a Bulgarian revolutionary organisation founded and built up by Bulgarian revolutionary Vasil Levski between 1869 and 1871.

The foundation of IRO reflected Levski's ideas that the centre of revolutionary activity be transferred from the Bulgarian emigrant circles in Romania to Bulgaria proper.

In 1871 Levski prepared the Charter of the organisation in the spirit of his own political views: liberation of Bulgaria from the Ottomans through a nationwide revolution and establishment of the country as a democratic republic with guarantees for the equality of all of its citizens regardless of their ethnicity or religion.

By the end of 1872, both Levski and Lyuben Karavelov, the chairman of the Bulgarian Revolutionary Central Committee (BRCC), which was situated in Bucharest, had concluded that the future success of the armed struggle against the Ottomans depended on the co-operation of both: external and internal committees.

To this end the two organisations prepared and adopted a joint programme and charter and voted on the merger of the two organisations under the name of BRCK at a general meeting held in Bucharest in May, 1872.