PARSHA-256 -- a new parallelizable hash function and a multithreaded implementation. In this paper, we design a new hash function PARSHA-256. PARSHA-256 uses the compression function of SHA-256 along with the Sarkar-Schellenberg composition principle. As a consequence, PARSHA-256 is collision resistant if the compression function of SHA-256 is collision resistant. On the other hand, PARSHA-256 can be implemented using a binary tree of processors, resulting in a significant speed-up over SHA-256. We also show that PARSHA-256 can be efficiently implemented through concurrent programming on a single processor machine using a multithreaded approach. Experimental results on P4 running Linux show that for long messages the multithreaded implementation is faster than SHA-256.