Masterbatch, rubber composition, and pneumatic tire

The present invention aims to provide a masterbatch which enables microfibrillated plant fibers to be well dispersed in a rubber composition so that they can provide reinforcement equal to or greater than that by conventional fillers; a rubber composition containing the masterbatch; and a pneumatic tire produced using the rubber composition. The present invention relates to a masterbatch containing a modified natural rubber with a phosphorus content of 200 ppm or less, and microfibrillated plant fibers. Preferably, the microfibrillated plant fibers in a primary form have an average fiber diameter of 4 nm to 10 µm and an average fiber length of 100 nm to 200 µm.