Abu Doaa el-Ansari, the leader of the Sinai-based militant group - Ansar Beit el-Maqdes - and 45 other militants, including some of his senior aides, were killed in el-Arish city of North Sinai in an operation by Egypt's armed forces, army spokesperson Brigadier General Mohamed Samir said in a statement.
Many others were injured in the army raid, Samir said.
Ansar Beit el-Maqdes had pledged allegiance to Islamic State militant group in 2014.
The attacks targeting police and military personnel increased after the ouster of Islamist ex-president Mohamed Morsi in 2013 following massive protests against his rule.
Over 700 security personnel have been reported killed since then.
The military has launched security operations in the area, arrested suspects and demolished houses that belong to terrorists, including those facilitating tunnels leading to the Gaza Strip.