The female part homologous to the penis is

In males, the penis is an erectile copulatory body. It is composed of three longitudinal cylindrical masses of erectile tissue. These include the right and left corpora cavernosa and the median corpus spongiosum. 

Similarly, in females, the clitoris is the erectile body. It is, however, made up of two masses of erectile tissue, i.e. two parallel corpora cavernosa.