This review discusses alternative and sustainable protein sources for pig diets, focusing on Spirulina, insect larvae (Tenebrio molitor and Hermetia illucens), rapeseed meal, and grain legumes. The study evaluates their nutritional value, effects on pig performance, digestion, immune system, and meat quality. It also addresses the limitations of their use in pig diets and potential treatments to enhance their nutritional value. Spirulina, a blue-green algae, is high in protein and nutrients, with a balanced amino acid profile. It can improve growth performance and meat quality in pigs. However, its cell wall is difficult for pigs to digest, and its use in diets may affect growth performance. Studies show that Spirulina can be beneficial when used in diets, but its effectiveness depends on factors like inclusion level and form. Insect larvae, particularly Tenebrio molitor and Hermetia illucens, are high in protein and have a high edible percentage. They are considered sustainable protein sources due to their efficient resource use and ability to convert organic waste into protein. However, their use in pig diets is limited by safety concerns, such as the presence of toxic substances like benzoquinone. Despite this, insect larvae can improve gut health and intestinal microbiota in pigs. Rapeseed meal and grain legumes, such as fava beans, peas, lupins, and chickpea, are potential protein sources for pigs. Rapeseed meal has a high protein content but contains anti-nutritional factors like glucosinolates and erucic acid, which can affect thyroid function and protein digestion. However, low-erucic acid and low-glucosinolate varieties of rapeseed have been developed to improve their safety and nutritional value. The study highlights the potential of these alternative protein sources to reduce reliance on soybean meal, improve sustainability, and enhance pig performance. However, further research is needed to optimize their use in pig diets and address safety and nutritional concerns.This review discusses alternative and sustainable protein sources for pig diets, focusing on Spirulina, insect larvae (Tenebrio molitor and Hermetia illucens), rapeseed meal, and grain legumes. The study evaluates their nutritional value, effects on pig performance, digestion, immune system, and meat quality. It also addresses the limitations of their use in pig diets and potential treatments to enhance their nutritional value. Spirulina, a blue-green algae, is high in protein and nutrients, with a balanced amino acid profile. It can improve growth performance and meat quality in pigs. However, its cell wall is difficult for pigs to digest, and its use in diets may affect growth performance. Studies show that Spirulina can be beneficial when used in diets, but its effectiveness depends on factors like inclusion level and form. Insect larvae, particularly Tenebrio molitor and Hermetia illucens, are high in protein and have a high edible percentage. They are considered sustainable protein sources due to their efficient resource use and ability to convert organic waste into protein. However, their use in pig diets is limited by safety concerns, such as the presence of toxic substances like benzoquinone. Despite this, insect larvae can improve gut health and intestinal microbiota in pigs. Rapeseed meal and grain legumes, such as fava beans, peas, lupins, and chickpea, are potential protein sources for pigs. Rapeseed meal has a high protein content but contains anti-nutritional factors like glucosinolates and erucic acid, which can affect thyroid function and protein digestion. However, low-erucic acid and low-glucosinolate varieties of rapeseed have been developed to improve their safety and nutritional value. The study highlights the potential of these alternative protein sources to reduce reliance on soybean meal, improve sustainability, and enhance pig performance. However, further research is needed to optimize their use in pig diets and address safety and nutritional concerns.