In recent years, the use of natural fibers as a reinforcement or filler in the construction of composites has attracted the attention of many researchers and different sectors of the industry. Compared to other competing reinforcements such as glass fibers and mineral fillers, these fibers have many advantages, such as being environmentally friendly, lower density, higher strength, and specific modulus, and easy to modify the fiber surface, and they are also widely available. These fibers are cheaper than synthetic fibers and can replace synthetic fibers in many applications where it is preferable to save on the resistance properties of the product. The fact that natural fibers are renewable plays an important role in the use of these materials in the future, and the increasing interest of consumers to buy environmentally friendly products has increased the need for industries to use natural materials. Therefore, there is a wide range of materials that can be used as fillers and reinforcements in the construction of composites, which can be wood particles and fibers, animal-based fibers, agricultural waste particles and fibers (linen fibers, hemp, bamboo, straw, and stubble, rice bran, etc.) were divided. Therefore, the comparative investigation of composite properties obtained from materials with different shapes (fibers or particles) can be considered one of the most important research activities to increase the added value of products and reduce costs. Humans have been using natural fibers for many years to make various parts. The use of straw in mud walls, bamboo fibers in the construction of boats, goat wool and horse tail hair together with flowers in the construction of ovens, and palm fibers in the construction of boats and shelters are different examples of the use of natural fibers in the construction of various products that mankind has developed throughout history. They have benefited. Even today, researchers’ serious attention to the use of natural fibers in the manufacture of advanced composite parts shows the importance of this category of fibers.