AbstractThis study aimed to measure the validity and reliability of the Inventory of Basic Religious Knowledge (IBRK) or in Malay, _Inventori Pengetahuan Asas Agama_. The IBRK questionnaire aimed to measure an individual_s fundamental knowledge of Islam based on four subscales, namely the purification of minor impurities, purification of major impurities, Adhan and Iqamah, and five-time prayer. The IBRK contains 50 items in which every subscale contains 10 items, and each of them consists of 5 positive items and 5 negative items; except for the five-times prayer subscale which contains 20 items, with 10 positive items and 10 negative items. The theoretical framework used for this study is a combination of the basics of Fardhu Ain and Fardhu Kifayah, which describes the specific knowledge and practices that are very important for every Muslim to practise in order to become an ideal Muslim. Six experts in the fields of religion, counselling and languages were selected to answer a specially desig.....