Bacteriophage f2 is an icosahedral, positive-sense single-stranded RNA virus that infects the bacterium Escherichia coli.

[1] It is closely related to bacteriophage MS2 and assigned to the same species.

[2] f2 was the first RNA-containing bacteriophage to be isolated, reported in 1961.

[3] Tim Loeb and Norton Zinder identified two phages in filtered samples of raw New York City sewage that grew on male (F+) but not on female (F−) E. coli.

The first phage f1, produced cloudy plaques, while the second phage, f2, produced clear plaques.