Saiful Islam or Saif al-Islam (Arabic: سيف الإسلام; "Sword of Islam"), may refer to:

• Khalid ibn al-Walid, general and companion to the Islamic prophet Muhammad
• Tughtakin ibn Ayyub, second Ayyubid emir of Yemen and Arabia between 1182 and 1197
• Saiful Islam Khan (1942–2019), Bangladeshi poet and literary critic
• Ahmed Seif El-Islam (1951–2014), Egyptian politician
• Abuhena Saifulislam (born 1963), imam chaplain in the US armed forces
• Saiful Islam (chemist) (born 1963), British chemist
• Saiful Islam (cricketer, born 1969) (born 1969), Bangladeshi cricketer
• Mohammad Saiful Islam (born 1970), Bangladeshi politician
• Saif al-Islam Gaddafi (born 1972), son of former Libyan leader Muammar Gaddafi
• Saiful Islam Mannu (born 1972), Bangladeshi film director
• Saiful Islam Al-Payage (born 1979), Indonesian preacher
• Shaiful Islam (born 1983), Bangladeshi cricketer
• Saiful Islam Hiru, Bangladeshi politician
• Saiful Islam (film editor), Bangladeshi film editor
• Saiful Islam Badal, Bangladeshi cinematographer
• Saiful Islam Joarder, Bangladeshi army fugitive
• Saiful Islam Duke, Bangladesh Navy lieutenant commander
• Saiful Islam (Natore politician), Bangladeshi advocate and politician
• Saiful Islam (electrical engineer), former vice-chancellor of Bangladesh University of Engineering and Technology
• Saif al-Islam al-Masri, Egyptian member of al-Qaeda

• The Sword of Islam, a 1987 British documentary film
• Sword of Islam (Mussolini), a ceremonial weapon given in 1937 to Benito Mussolini

• Sayf al-Din (disambiguation)