Fibrous cellulose, fibrous cellulose dispersion, and fibrous cellulose production method

A fibrous cellulose dispersion liquid obtained by dispersing a fibrous cellulose having a fiber width of 1,000 nm or less and containing an ionic substituent in a solvent containing water,

• wherein an amount of the ionic substituent in the fibrous cellulose is 0.10 mmol/g or more and 1.50 mmol/g or less,
• a polymerization degree of the fibrous cellulose is 150 or more and 515 or less, and
• when the fibrous cellulose is dispersed in a dispersion solvent containing water and isopropanol to obtain a dispersion liquid having a 7:3 mass ratio of water and isopropanol and a viscosity of 2,500 mPa·s at 23° C., and the dispersion liquid is stirred under following stirring conditions, a viscosity change rate falls within ±50% as calculated by following formula:
• viscosity change rate (%)=(viscosity after stirring−viscosity before stirring)/viscosity before stirring×100
• (stirring conditions)
• the dispersion liquid having the viscosity of 2,500 mPa·s at 23° C. is poured into a cylindrical container having a diameter of 10 cm to a height of 5 cm, and is stirred at 23° C. for 24 hours by using an elliptical stirrer having a length of 5 cm, a center width of 2 cm, and an end width of 1 cm, while maintaining a 2 cm-recessed state at a center of a liquid surface,
• wherein when the dispersion liquid with 0.4% by mass of the fibrous cellulose is formed through dispersion in water, the viscosity of the dispersion liquid at 23° C. is 20 mPa·s or more and 4,700 mPa·s or less, and a polymerization degree of the microfibrous cellulose is 320 or more and 515 or less.