There are several options. Many public domain websites have a collection of free online novels. Also, some authors offer their works for free on their personal blogs or websites. For example, Archive.org has a decent selection.
You could look on platforms like ManyBooks. They have a wide range of free novels across different genres. Another option is to search for specific authors' websites, as some release free content there. Just be sure to check the legality of the source.
You can try some well-known websites like Project Gutenberg or Wattpad. They offer a variety of free novels.