Ansar ul Islam or Ansar al-Islam (Arabic: انصار الاسلام; "Partisans of Islam" or "Helpers of Islam") may refer to:
- Ansar al-Islam in Kurdistan, a Kurdish Salafist group in Northern Iraq and Syria
- Ansar al-Islam (Bangladesh) also called Ansarullah Bangla Team, a radical islamist group in Bangladesh
- Ansar ul-Islam (Pakistan), a Barelvi Sunni Muslim group in the Khyber Agency, Federally Administered Tribal Areas, Pakistan
- Ansarul Islam (Kashmir), founded in 1983 and merged into Hizbul Mujahideen in 1989
- Ansarul Islam (Sahel), an organization in Burkina Faso and Mali
- Jabhat Ansar al-Islam, Syrian rebel group