The Intelligence Bureau (IB) (Hindi: आसूचना ब्यूरो; IAST: āsūcanā byūro) is India's internal security and counterintelligence agency under the Ministry of Home Affairs.

To reduce expenses, the agency shared the manpower and facilities of the existing Thuggee and Dacoity Department, headquartered at Shimla.

[7] The Provincial Special Branches were attached to the offices of either the Inspector General of Police or the chief secretary of the respective provinces.

[8] This reorganization led to the abolition of the Thuggee and Dacoity Department and the merger of the Central Special Branch into the DCI.

Initially, Provincial Special Branches were incorporated into the CIDs, headed by a Deputy Inspector General (DIG), but they were later separated as their functions evolved.

Reflecting this directive, the DCI was renamed the Intelligence Bureau in 1920, a year before the Act formally came into force in 1921.

[11] The IB, initially also referred to as the Delhi Intelligence Bureau (DIB), was placed under the Home Department and reported directly to the Governor-General of India.

After India gained independence in 1947, the IB came under the Ministry of Home Affairs, with T. G. Sanjeevi Pillai becoming its first Indian director.

[15] The IB functions under the Ministry of Home Affairs and is headed by a Director of the Intelligence Bureau.

The IB maintains field units and headquarters, usually under the control of Joint or Deputy Directors.

[2] Shrouded in secrecy, the IB is used to garner intelligence from within India and also execute counter-intelligence and counter-terrorism tasks.

All spheres of human activity within India and in the neighbourhood are allocated to the charter of duties of the Intelligence Bureau.

The IB was also tasked with other external intelligence responsibilities from 1951 until 1968 when the Research and Analysis Wing was formed.

The external intelligence branch was handed to the newly created the Research and Analysis Wing.

[22] Heavy politics, under-funding and a shortage of field agents were the chief problems facing the agency.