拉普拉斯变换（英语：Laplace transform）是应用数学中常用的一种积分变换，又名拉氏转换，其符号为。拉氏变换是一个线性变换，可将一个有引数实数t（t ≥ 0）的函数转换为一个引数为复数s的函数：

拉氏变换在大部份的应用中都是对射的，最常见的f(t)和F(s)组合常印制成表，方便查阅。拉普拉斯变换得名自法国天文学家暨数学家皮埃尔-西蒙·拉普拉斯（Pierre-Simon marquis de Laplace），他在机率论的研究中首先引入了拉氏变换。

拉氏变换和傅里叶变换有关，不过傅里叶变换将一个函数或是信号表示为许多弦波的叠加，而拉氏变换则是将一个函数表示为许多矩的叠加。拉氏变换常用来求解微分方程及积分方程。在物理及工程上常用来分析线性非时变系统，可用来分析电子电路、谐振子、光学仪器及机械设备。在这些分析中，拉氏变换可以作时域和频域之间的转换，在时域中输入和输出都是时间的函数，在频域中输入和输出则是复变角频率的函数，单位是弧度每秒。

In mathematics the Laplace transform is an integral transform named after its discoverer Pierre-Simon Laplace (/ləˈplɑːs/). It takes a function of a positive real variable t (often time) to a function of a complex variable s (frequency).

The Laplace transform is very similar to the Fourier transform. While the Fourier transform of a function is a complex function of a real variable (frequency), the Laplace transform of a function is a complex function of a complex variable. Laplace transforms are usually restricted to functions of t with t > 0. A consequence of this restriction is that the Laplace transform of a function is a holomorphic function of the variable s. Unlike the Fourier transform, the Laplace transform of a distribution is generally a well-behaved function. Also techniques of complex variables can be used directly to study Laplace transforms. As a holomorphic function, the Laplace transform has a power series representation. This power series expresses a function as a linear superposition of moments of the function. This perspective has applications in probability theory.