A reinforcing aluminum-based filler which can be used for reinforcing diene rubber compositions intended for the manufacture of tires, comprising an aluminum (oxide)hydroxide corresponding, with the exception of any impurities and the water of hydration, to the general formula (a and b being real numbers):

the specific BET surface area of which is between 30 and 400 m²/g, the average particle size (by mass) d_w of which is between 20 and 400 nm and the disagglomeration rate, , of which, measured via an ultrasound disagglomeration test at 100% power of a 600-watt ultrasonic probe, is greater than 510^-3 m^-1/s is provided. A rubber composition suitable for the manufacture of tires comprising said aluminum-based filler as reinforcing filler.