C

#include <stdio.h>

int main(void)
{
    printf("Hello, world!");
    return 0;
}

C++

#include <iostream>

int main(void)
{
    std::cout << "Hello, world!";
    return 0;
}

Java

class HelloWorld {
    static public void main( String args[] ) {
        System.out.println( "Hello, world!" );
    }
}

Go

package main

import "fmt"

func main() {
    fmt.Println("Hello, world!")
}

PHP

echo 'Hello, world!';

Perl

print "Hello, world!";

Python

'Hello, world!';

Ruby

puts 'Hello, world!'

Delphi

program HelloWorld;

begin
    WriteLn('Hello, world!');
end.

Rust

fn main() {
    println!("Hello, world!");
}

Assembler

section .data
    msg db 'Hello, world!', 0xA
    len equ $ - msg

section .text
    global _start

_start:
    mov eax, 4
    mov ebx, 1
    mov ecx, msg
    mov edx, len
    int 0x80


    mov eax, 1
    xor ebx, ebx
    int 0x80

JavaScript

console.log('Hello, world!');

Lua

print("Hello, world!")