This review examines the nutritional and anti-nutritional factors of Spirulina, insect larvae (Tenebrio molitor and Hermetia illucens), rapeseed meal, and grain legumes (fava beans, peas, lupins, and chickpeas) to evaluate their potential as alternative protein sources in pig diets. The effects of these ingredients on pig performance, digestion, immune system, and the physicochemical and sensorial characteristics of pork are discussed. The review also revisits the limitations of using these ingredients in pig diets and suggests possible treatments to enhance their nutritional value. Key findings include: 1. **Spirulina**: High in protein and lipids, with a balanced composition of amino acids, vitamins, minerals, and essential fatty acids. It has been shown to improve growth performance and meat quality in various animals, but its cell wall carbohydrates are difficult for monogastric animals to digest. 2. **Insect Larvae**: High in protein and fat, with a digestibility and functionality profile that makes them a sustainable alternative to soybean meal. Insects like Tenebrio molitor and Hermetia illucens can be used at up to 6% and 10% in weaning and growing pig diets, respectively, without negative effects. They can improve growth performance, feed intake, nutrient digestibility, and intestinal health. 3. **Rapeseed Meal**: A by-product of oil and biofuel production, with a crude protein content of 33.7-35.6%. While it has high fiber and anti-nutritional factor content, modern varieties with lower levels of erucic acid and glucosinolates are available, making it a viable alternative. 4. **Grain Legumes**: Contain protein, fiber, starch, and various nutrients. They are low in sulfur-containing amino acids and tryptophan compared to soybean meal but can be used to diversify diets. However, their use is limited by the presence of anti-nutritional factors such as tannins, protease inhibitors, and alkaloids. The review highlights the need for further research to optimize the use of these alternative protein sources in pig diets, addressing issues such as digestibility, safety, and the integration of essential nutrients.This review examines the nutritional and anti-nutritional factors of Spirulina, insect larvae (Tenebrio molitor and Hermetia illucens), rapeseed meal, and grain legumes (fava beans, peas, lupins, and chickpeas) to evaluate their potential as alternative protein sources in pig diets. The effects of these ingredients on pig performance, digestion, immune system, and the physicochemical and sensorial characteristics of pork are discussed. The review also revisits the limitations of using these ingredients in pig diets and suggests possible treatments to enhance their nutritional value. Key findings include: 1. **Spirulina**: High in protein and lipids, with a balanced composition of amino acids, vitamins, minerals, and essential fatty acids. It has been shown to improve growth performance and meat quality in various animals, but its cell wall carbohydrates are difficult for monogastric animals to digest. 2. **Insect Larvae**: High in protein and fat, with a digestibility and functionality profile that makes them a sustainable alternative to soybean meal. Insects like Tenebrio molitor and Hermetia illucens can be used at up to 6% and 10% in weaning and growing pig diets, respectively, without negative effects. They can improve growth performance, feed intake, nutrient digestibility, and intestinal health. 3. **Rapeseed Meal**: A by-product of oil and biofuel production, with a crude protein content of 33.7-35.6%. While it has high fiber and anti-nutritional factor content, modern varieties with lower levels of erucic acid and glucosinolates are available, making it a viable alternative. 4. **Grain Legumes**: Contain protein, fiber, starch, and various nutrients. They are low in sulfur-containing amino acids and tryptophan compared to soybean meal but can be used to diversify diets. However, their use is limited by the presence of anti-nutritional factors such as tannins, protease inhibitors, and alkaloids. The review highlights the need for further research to optimize the use of these alternative protein sources in pig diets, addressing issues such as digestibility, safety, and the integration of essential nutrients.