This study explores the biography and methodology of the English orientalist Thomas Arnold (18641930), who is regarded as one of the most prominent scholars in Islamic and Arabic studies. Arnold began his academic career in India, where he worked as a professor of philosophy at Aligarh Muslim University and was deeply influenced by Islamic culture during his time there. He later moved to London, where he held the position of Professor of Arabic and Islamic Studies at the University of London and served as the director of the Institute of Oriental Studies.Arnold was distinguished by his impartial approach to the study of Islam, striving to present a balanced view of the Islamic religion and civilization, free from the biases prevalent in his era. Among his most notable works is the book The Preaching of Islam, which examines the historical spread of Islam, focusing on the issue of religious tolerance in Islamic tradition. Another significant work is The Caliphate, where he traces the history of the caliphate institution from the era of the Rightly Guided Caliphs to its abolition by Mustafa Kemal Atatrk in 1924.Despite his efforts to provide a fair portrayal of Islam, Arnold's methodology was not devoid of certain biases and methodological errors, particularly in The Caliphate, where he relied heavily on orientalist sources without adequately balancing them with original Islamic sources. Nevertheless, Arnold remains one of the most influential orientalists who contributed significantly to enriching Islamic studies in the West.