Nginx not starting: Address already in use (nginx: bind to 0.0.0.0:80 failed)

Hi all,

I just installed Nginx but when I try to start it it fails with the following error:

nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)

If I check the status I get the following output:

● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; disabled; vendor preset: enabled)
  Drop-In: /etc/systemd/system/nginx.service.d
           └─override.conf
   Active: failed (Result: exit-code) since Mon 2020-06-08 15:59:32 UTC; 5min ago
     Docs: man:nginx(8)
  Process: 3839 ExecStop=/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid (code=exited, status=2)
  Process: 3816 ExecStartPost=/bin/sleep 0.1 (code=exited, status=0/SUCCESS)
  Process: 25445 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=1/FAILURE)
  Process: 25435 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
 Main PID: 3813 (code=exited, status=0/SUCCESS)

Jun 08 15:59:30 ubuntu nginx[25445]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jun 08 15:59:30 ubuntu nginx[25445]: nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
Jun 08 15:59:31 ubuntu nginx[25445]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jun 08 15:59:31 ubuntu nginx[25445]: nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
Jun 08 15:59:31 ubuntu nginx[25445]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Jun 08 15:59:31 ubuntu nginx[25445]: nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
Jun 08 15:59:32 ubuntu nginx[25445]: nginx: [emerg] still could not bind()
Jun 08 15:59:32 ubuntu systemd[1]: nginx.service: Control process exited, code=exited status=1
Jun 08 15:59:32 ubuntu systemd[1]: nginx.service: Failed with result 'exit-code'.
Jun 08 15:59:32 ubuntu systemd[1]: Failed to start A high performance web server and a reverse proxy server.

Does anyone have any ideas why Nginx would not start?

Thanks!