This dissertation is the first ever which provides an annotated translation and analysis of the Gaṇitatilaka by Śrīpati and its Sanskrit commentary by the Jaina monk Siṃhatilakasūri (14th century CE). The Gaṇitatilaka is a Sanskrit mathematical text written by Śrīpati, an astronomer-mathematician who hailed from 11th century CE Maharashtra. It has come down to us together with Siṃhatilakasūri’s commentary in a uniquely extant yet incomplete manuscript. The only edition available of both Sanskrit texts is by Kāpadīā (1937). Siṃhatilakasūri’s commentary upon the Gaṇitatilaka GT is a precious source of information on medieval mathematical practices. To my knowledge, this is, in fact, the first Sanskrit commentary on mathematics –whose author is known– that has survived to the present day and the first written by a Jaina that has come down to us. This work has never before been studied or translated into English. It is my intention to show that the literary practices adopted by Siṃhatilakasūri, in expounding step-by-step Śrīpati’s work, enrich the commentary in such a way that it consequently becomes “his own mathematical text.” Together with the English translation of both the root-text by Śrīpati and the commentary by Siṃhatilakasūri, I present the reconstruction of all the mathematical procedures explained by the commentator so as to understand the way medieval Indian mathematics was carried out. I also investigate Siṃhatilakasūri’s interpretative arguments and the interaction between numbers and textual norms which characterises his work. The present research aims to: i) edit the Sanskrit edition by Kāpadīā ii) revise the English translation of Śrīpati’s text by Sinha (1982) iii) provide the first annotated English translation of selected passages from the commentary by Siṃhatilakasūri iv) highlight the contribution to our understanding of the history of Indian mathematics brought by this commentary and v) investigate Siṃhatilakasūri’s literary style.