Template:Sister project Quasilinear may refer to:
- Quasilinear function, a function that is both quasiconvex and quasiconcave
- Quasilinear utility, an economic utility function linear in one argument
- In complexity theory and mathematics, quasilinear time O(n (log n)k), or sometimes more specifically O(n log n)
- Quasilinear equation, a type of differential equation; see Partial differential equation#Linear and nonlinear equations