Cost / License
- Free
- Open Source
Application type
Platforms
- Mac
- Windows
- Linux
- BSD
- Rust

One of the most popular alternatives to C# is Python, which is free and open source. Other popular alternatives are Java, Rust, C++ and C (programming language). There's no shortage of Programming Languages like C#, with more than 50 alternatives for Linux, Windows, Mac, the web and self-hosting.

Hy is a wonderful dialect of Lisp that’s embedded in Python.
Since Hy transforms its Lisp code into the Python Abstract Syntax Tree, you have the whole beautiful world of Python at your fingertips, in Lisp form!.
Beef is an open source performance-oriented compiled programming language which has been built hand-in-hand with its IDE environment.

M# is a set of tools for rapid web application development. M# manages 90% of the code through automation and eliminates most human errors. It has been proven to result in better, safer, and more reliable code, at least 4X faster.

Vala is a new programming language that aims to bring modern programming language features to GNOME developers without imposing any additional runtime requirements and without using a different ABI compared to applications and libraries written in C.
Tcl (Tool Command Language) is a very powerful but easy to learn dynamic programming language, suitable for a very wide range of uses.

C3 is a programming language that builds on the syntax and semantics of the C language, with the goal of evolving it while still retaining familiarity for C programmers.
Smalltalk is an object-oriented programming (OOP) language. It is objects all the way down. Smalltalk’s purity and clarity in this regard made it the archetype for nearly all other OOP languages.

Squirrel is a high level imperative, object-oriented programming language, designed to be a light-weight scripting language that fits in the size, memory bandwidth, and real-time requirements of applications like video games.
Object Pascal is a multi-paradigm, object-oriented, component-based general purpose programming language.
Temper is a programming language and toolchain for making libraries that can be used natively from any other language.