The Shachi-class (Project 21) was a class of naval offshore patrol vessels supposed to be built by Reliance Defence and Engineering (formerly known as Pipavav Defence and Offshore Engineering Company Limited) at its shipyard in Indian state of Gujarat.

[5] However, talks with Severnoye broke down over differences in pricing and a new design partner, reported to be Alion Science, was chosen.

[8][9] In DEFEXPO 2014, Pipavav shipyard released a new design for the class with a lower displacement of 1,500 tonnes (1,500 long tons) but a higher top speed of 46 km/h (25 knots).

[10] In June 2016, it was reported that the shipyard is accelerating work on the delayed order with a shorter delivery schedule for the last three ships.

[13] In October 2020, the Indian Navy cancelled the deal to acquire offshore petrol vessels due to 10 year delay in their delivery and the heavy indebtedness of the contractor.