The J -I was a Japanese carrier rocket. There was only one test flight.

This was the first missile that was jointly developed by ISAS and NASDA. As the first stage a solid rocket boosters of the H- II was used, the second and the third derived from M- 3SII. There were plans for two test flights with two or three levels and at least one operational launch. However, there was only one test launch on 11 February 1996, two stages, the rocket reached an apogee of 110 km.

After that, the NASDA withdrew the project support, as the cost of developing the missile turned out to be much more expensive than similar projects in other countries. The JI should complement of the payload forth the Mu -V, but the starting price of 52 million U.S. dollars for just 1000 kg were to be disproportionate, since comparable American carrier rockets, such as Taurus or Athena only 12 to 16 million U.S. dollars cost.