A room‐temperature‐stable crystalline cyclic (alkyl)(amino)nitrenium cation 2 features cationic nitrogen atom with a smaller HOMO–LUMO gap compared to that of a 1,2,3‐triazolium 5 (an N‐heterocyclic nitrenium cation). The low‐lying LUMO of 2 results in an enhanced electrophilicity, which allowed for the formation of Lewis adducts with neutral Lewis bases, such as Me3P, nBu3P, and IiPr. The N‐based Lewis acid 2 also forms an FLP with tBu3P but subsequently reacts with (PrS)2 to cleave the S−S bond. Both experimental and theoretical results suggest that the Lewis acidity of 2 is stronger than its N3 analogues.