This book includes biographical entries on internationally renowned Mathematicians who have made important contributions towards the development of Mathematics. An attempt has been made to select these mathematicians from ancient times to the 20th century. The entries include biographical data, place and date of birth, post held, etc. but do not furnish personal details about the subject's family, prizes, honorary degrees, etc. However, a sincere effort has been undertaken to include their main research achievements, discoveries and inventions but the nature and importance of some entries are somewhat lengthy because we have found taken them interesting. It is hoped that the readers will find entries useful and interesting. The book will be of immense value to the students of Mathematics, research scientists and engineers working in science projects.