Syed Ahmad Dehlavi (died 1894) was an Indian Muslim academician and hadith scholar who served as the second principal and Sheikh al-Hadith of Darul Uloom Deoband between 1884 and 1890. He specialised in Islamic astronomy and mathematics. His students included Abdul Hayy Hasani, Murtaza Hasan Chandpuri, Mahmud Hasan Deobandi, Aziz-ul-Rahman Usmani, Muhammad Yasin Deobandi, Ubaidullah Sindhi, and Ashraf Ali Thanwi.
Syed Ahmed Dehlvi belonged to a Sayyid family in Delhi. His father, Maulvi Imamuddin, privately tutored Mughal princes, and his maternal uncle, Mir Syed Mehboob Ali Jafari, was a student of Shah Abdul Aziz Dehlavi.
Syed pledged allegiance to Qasim Nanawtawi in Sufism. In 1868 AD (1285 AH), he began his career as a teacher at Darul Uloom Deoband and succeeded Yaqub Nanautawi as the seminary's second principal and Sheikh al-Hadith (Senior Professor of Hadith) in 1886 (Rabi' al-Thani 1302 AH). He resigned from the seminary in 1890 AD (1307 AH) and joined Madrasa Jahangiri in Bhopal as a principal and rector at the invitation of Shah Jahan Begum.
During his tenure as principal at Darul Uloom Deoband, thirty students completed graduation in Dars-e-Nizami, including Ghulam Rasool Hazarvi and Murtaza Hasan Chandpuri. Mahmud Hasan Deobandi, Muhammad Yasin Deobandi, Ubaidullah Sindhi, Aziz-ul-Rahman Usmani, Ashraf Ali Thanwi, and Abdul Hayy Hasani were also among his students in Deoband and Bhopal, respectively.
He died in Bhopal in 1894 (1311 AH).