Nearest neighbor may refer to:
- Nearest neighbor search in pattern recognition and in computational geometry
- Nearest-neighbor interpolation for interpolating data
- Nearest neighbor graph in geometry
- The k-nearest neighbor algorithm in machine learning, an application of generalized forms of nearest neighbor search and interpolation
- The nearest neighbour algorithm for approximately solving the travelling salesman problem
- The nearest neighbor method for determining the thermodynamics of nucleic acids
- The nearest neighbor method for calculating distances between clusters in hierarchical clustering.