If you download the game, I highly recommend installing the community patch. It fixes bugs, adds widescreen support, and stabilizes the multiplayer, which is essential for a smooth experience on a modern PC.
While you may see "free download" links on various sites, many are outdated or contain security risks. Since the game is now "abandonware" in spirit but still commercially available, the best way to get a stable, full version that works on modern Windows (10/11) is through digital storefronts:
Occasionally featured in sales or bundles. The "Free" Factor
The Geo-Mod engine lets you create your own paths by tunneling through rock or collapsing structures on enemies.
You play as Parker, a miner joining a revolution against the oppressive Ultor Corporation.
Red Faction has been given away for free during special GOG anniversary events in the past.