Interrogative pronouns in Japanese grammar are essential elements when forming questions. They help learners inquire about specific information such as people, places, objects, and amounts. Common interrogative pronouns in the Japanese language include だれ (who), なに/なん (what), どれ/どの (which), and いくつ (how many). Understanding and using these pronouns correctly is crucial for learners as they navigate the Japanese language and engage in conversations with native speakers.