注册机（英语：Keygen或Keymaker），又称序号机、序号产生器、注册码生成器、串行号生成器，为一种可破解商业软件注册进程之程序。

大部分注册机可根据用户输入注册内容来生成对应注册序号或注册文件。与此同时，也有很多程序不需输入用户名或其他信息即可获得注册时所需之序号。制作注册机者多为黑客或少数本地化作者。一般需要脱壳软件、内存查看软件和反汇编器等破解工具作为辅助。

为维护自身权益，部份软件公司采用机器码或软件分试用版和商业版等方式，以抵制注册机。同时某些新发行软件使用启动机制以试图阻止盗版，然而仍遭注册机破解。

The Keymaker is a fictional character, portrayed by Korean-American actor Randall Duk Kim, in the 2003 film The Matrix Reloaded. He is a computer program that can create shortcut commands, physically represented as keys, which can be used by other programs to gain quick access to various areas within the simulated reality of the Matrix. He appears as an elderly, bespectacled Asian man dressed in a button-down shirt, smock, and an apron hung with bunches of keys.