Peroxynitrite ($(ONOO^-)$ is a cytotoxic species formed from nitric oxide and superoxide anion, which are highly implicated in the pathogenesis of oxidative stress-mediated diseases. The aim of this study was to investigate the scavenging effects of Phellinus linteus on authentic $ONOO^-$, and further phytochemical studies are planned that will attempt to identify the active principles. From the active EtOAc fraction, a mixture of fungisterol and 5-dihydroergosterol (1), a mixture of betulin and 1,2-benzenedicarboxylic acid bis (2-methyl heptyl) ester (2), protocatechualdehyde (3), protocatechuic acid (4), cirsiumaldehyde (5), hispidin (6), caffeic acid (7), phelligridin D (8), uracil (9), gallic acid (10), 2,5-dihydroxybenzoic acid (11), ferulic acid (12), 2,3-dihydroxybenzaldehyde (13), arbutin (14), isoferulic acid (15), guanosine (16), and ellagic acid (17) were isolated, and their structures were characterized based on spectroscopic data. All compounds except 3, 6, 7 and 16 were isolated for the first time from P. linteus. Compounds 3, 4, 6-8, 10-15, and 17 showed potent scavenging activity on $ONOO^-$, with $IC_{50}$ values of $2.06;{pm};0.10$, $3.45;{pm};0.57$, $0.71;{pm};0.05$, $2.78;{pm};0.36$, $5.42;{pm};0.26$, $1.13;{pm};0.02$, $1.82;{pm};0.17$, $0.91;{pm};0.19$, $1.59;{pm};0.09$, $1.88;{pm};0.07$, $1.22;{pm};0.37$, and $2.01;{pm};0.02;{mu}M$, respectively, as compared to the positive control, DL-penicillamine, with an $IC_{50}$ value of $5.04;{pm};0.06;{mu}M$.