Afonso Henrique da Costa Guimarães, known as Alphonsus de Guimaraens; (July 24, 1870 in Ouro Preto – July 15, 1921 in Mariana) was a Brazilian poet.

The poetry of Alphonsus de Guimaraes is substantially mystical and involved with Catholicism. His sonnets display a classical structure, and are profoundly religious. They become increasingly sensitive as he explores the meaning of death, of the impossible love, of solitude and of his inadequacy regarding the world. However, the mystical tone marks in his works a feeling of acceptance and of resignation towards life, suffering and pain. Another characteristic aspect of his work ids the use of spirituality in relation to the feminine figure, which is considered to be an angel, or a celestial being. As a result of that, Guimaraes shows himself not one as a Symbolist but also a follower of Neo-romanticism.

His works, predominantly poetic, made him one of the main Symbolist authors in Brazil. In reference to the city he spent most of his life in, he is also called the "loner of Mariana", his "ivory tower of Symbolism" ("o solitário de Mariana" and "torre de marfim do Simbolismo", respectively, in Portuguese).