Oscar Horta (born Óscar Horta Álvarez; 7 May 1974) is a Spanish animal activist and moral philosopher. He is a professor in the Department of Philosophy and Anthropology at the University of Santiago de Compostela and a co-founder of the nonprofit organisation Animal Ethics. Active in vegan and antispeciesist advocacy since the mid-1990s, Horta has worked with several Spanish animal rights groups and has served on the advisory boards of international organisations concerned with animal ethics and suffering.

Horta's work addresses speciesism, animal ethics, and the moral status of sentient beings. He has argued for the moral consideration of all sentient beings and for responsible intervention in nature to reduce suffering among wild animals. In 2022, he published his first book in English, Making a Stand for Animals.

Horta completed an undergraduate degree in philosophy at the University of Santiago de Compostela (USC) in 1999, and a doctorate in philosophy at the same institution in 2007. His thesis was entitled Un desafío para la bioética: la cuestión del especismo ("A Challenge to Bioethics: The Issue of Speciesism"). In 2007, he won the Ferrater Mora Prize from the Oxford Centre for Animal Ethics for his essay on the ethics of the Catalan philosopher José Ferrater Mora.

Horta has been active in vegan and antispeciesist advocacy since the mid-1990s.

From 2005 to 2009, Horta was a lecturer in the Department of Logic and Moral Philosophy at USC. He was a visiting researcher at Rutgers University from 2009 to 2010 and held a research fellowship at the Spanish Foundation for Science and Technology from 2009 to 2011. He returned to USC in 2011 as a lecturer in the Department of Philosophy and Anthropology, becoming a professor in 2018.

Horta co-founded the animal advocacy organisation Animal Ethics in 2012. He has also acted as an organiser and spokesperson for the Spanish animal rights organisations Derechos para los Animales ("Rights for Animals") and Alternativa para la Liberación Animal ("Alternative for Animal Liberation"); these organisations later merged to form Equanimal.

Horta is a member of the advisory board for the Sentience Institute, UPF-Centre for Animal Ethics, and Organisation for the Prevention of Intense Suffering.

In 2022, Horta published Making a Stand for Animals, his first English-language book. It examines ethical questions concerning human attitudes and behaviour toward nonhuman animals. The book focuses on speciesism, the use of animals by humans, wild animal suffering, and the moral implications of extending consideration to all sentient beings.