The world's smallest fish depends on the measurement used.^[1]

Based on minimum standard length at maturity the main contenders are Paedocypris progenetica where females can reach it at 7.9 mm (0.31 in),^[2][3][4] the stout infantfish (Schindleria brevipinguis) where females reach it at 7 mm (0.28 in) and males at 6.5 mm (0.26 in),^[1] and Photocorynus spiniceps where males can reach it at 6.2 mm (0.24 in), but are attached to the far larger females.^[5][6] If judging smallest based on the species' maximum size (a measurement often used for fish), Paedocypris progenetica, dwarf pygmy goby (Pandaka pygmaea), midget dwarfgoby (Trimmatom nanus) and the stout infantfish (Schindleria brevipinguis) are not known to exceed 11 mm (0.43 in) in standard length,^[4][7][8][9] and the two Leptophilypnion sleeper gobies are less than 10 mm (0.39 in).^[10] A level of uncertainty about the full size range exists for some of these, as only a few specimens have been measured.^[10]

Little or no data is available on weight of most of these, but at less than 1 milligram (0.001 g) it is likely that the stout infantfish (Schindleria brevipinguis) is the smallest if using this feature.^[1]

List of smallest fish in the world

Image	Common Name	Species	Family	Standard length of smallest known mature individual	Maximum known standard length
		Paedocypris progenetica	Cyprinidae	7.9 mm (0.31 in), female[4]	10.3 mm (0.41 in)[4]
		Danionella translucida	Cyprinidae	10 mm [11]	15 mm[11]
		Danionella cerebrum	Cyprinidae	10 mm[11]	12.6 mm[11]
		Leptophilypnion fittkaui	Eleotridae	?	9.5 mm (0.37 in)[10]
		Leptophilypnion pusillus	Eleotridae	?	9.1 mm (0.36 in)[10]
	Dwarf pygmy goby	Pandaka pygmaea	Gobiidae	9 mm (0.35 in), male[7]	11 mm (0.43 in)[7]
	Midget dwarfgoby	Trimmatom nanus	Gobiidae	10 mm (0.39 in)[8]	10 mm (0.39 in)[8]
		Photocorynus spiniceps	Linophrynidae	6.2 mm (0.24 in), male[5]	50.2 mm (1.98 in), female far larger than male and species not among smallest by maximum standard length[5]
	Stout infantfish[12]	Schindleria brevipinguis	Gobiidae	6.5 mm (0.26 in), male[1]	10 mm (0.39 in)[9]