of the immunoproteasome has been associated with autoimmune diseases, inflammatory diseases, and various types of cancer. Selectiveinhibitors of the immunoproteasome are not only scarce, but also almost entirely restricted to peptide‐based compounds. Herein, we describe nonpeptidic reversible inhibitors that selectively block the chymotrypsin‐like (β5i) subunit of the human immunoproteasome in the