CityHash is a family of non-cryptographic hash functions, designed for fast hashing of strings. It has 32-, 64-bit variants. CityHash been referenced widely in academic papers.

Google developed the algorithm in-house starting in 2010. The authors expect the algorithm to outperform previous work by a factor of 1.05 to 2.5, depending on the CPU and mix of string lengths being hashed. CityHash is influenced by and partly based on MurmurHash.

Some particularly fast CityHash functions depend on CRC32 instructions that are present in SSE4.2. However, most CityHash functions are designed to be portable, though they will run best on little-endian 32-bit or 64-bit CPUs.

Google has announced FarmHash as the successor to CityHash.