There are many trails in Chilean Patagonia that you can do without a guide, provided you have experience with backcountry hiking and navigating. Whether you need a guide in Argentina is heavily dependent on the trail you choose. While some trails are well-marked, well-trafficked, and overall doable self-guided, it is highly recommended that you hire a guide for the more technical and/or remote treks, like the O Circuit or Huemul Circuit.