Phytochemical investigation of the methanolic extract of Cyperus rotundus L. (Cyperaceae) rhizomes afforded a new norterpenoid with an unprecedented carbon skeleton, namely cyperalin A (1) and sugetriol triacetate (2). Their structures were identified by using advanced spectroscopic technique such as UV, IR, 1D (1H and 13C), 2D (1H-1HCOSY, HSQC, HMBC, and NOESY) NMR, and HRESIMS as well as comparison with literature data. The isolated compounds were evaluated for their anti-inflammatory activity. Compound 1 displayed the highest inhibitory activity of PGE2, COX-2, and LOX-5 with IC50s 0.22, 1.03, and 1.37 µM, respectively compared to indomethacin (IC50s 0.15, 0.69, and 0.81 μM, respectively). Moreover, 2 demonstrated significant activity with IC50s 0.57 (PGE2), 1.74 (COX-2) and 2.03 (LOX-5) μM.