5 Rook / 9.2x27mmR is an obsolete centerfire rifle cartridge.

5 Rook is a straight rimmed cartridge originally designed for hunting small game and target shooting in rook rifles, although it was also used as a pistol cartridge.

5 Rook was introduced between 1875 and 1880 by lengthening the older .380 Long cartridge.

[2] This cartridge was initially available in both 134 gr (8.7 g) rifle loadings and 125 gr (8.1 g) pistol loadings, both cartridges being interchangeable.

5 Rook was superseded as a small game hunting and target cartridge by the .22 Long Rifle.