A liquid discharge head substrate includes a base; a pair of wiring lines; a heat-generating resistive layer, which is in contact with the wiring lines, and which has a portion corresponding to a space between the wiring lines, the portion forming an electrothermal transducer; an insulating layer which covers the heat-generating resistive layer and the wiring lines and which contains Si; a protective layer which covers at least one region of the insulating layer which contains Ir; and an intermediate layer which is placed between the insulating layer and the protective layer. The intermediate layer contains a material represented by the formula TaxSiyNz, where x is 5 atomic percent to 80 atomic percent, y is 3 atomic percent to 60 atomic percent, z is 10 atomic percent to 60 atomic percent.