Almeida was born in Lisbon in 1934. She was the daughter of the sculptor Leopoldo de Almeida (1898–1975). In 1955, Almeida completed the painting course at the School of Fine Arts in Lisbon. She married architect Artur Rosa. Their daughter Joana Rosa became an artist. After spending some years raising her family, in 1964 she obtained a scholarship and moved to Paris.
Almeida exhibited for the first time in 1967. At this exhibit she pioneered the use of three-dimensional elements in her work, a theme she would come back to often in her later pieces. She wanted her work to escape the canvas and intrigue the viewer.
Starting in 1969, Almeida defined a new aspect of her work, the desire for self-representation, in an exhibit which became the basis of her future work. She exhibited a black and white photograph of herself wearing a canvas, arms spread and looking down – as in Christ carrying the cross. This photograph asserted her belief in "identifying herself with the being of her work." This became an ongoing theme in her work: there is no difference between the work and artist's body. In her work, a woman's image is always present, but the image is transformed in a painting or drawing. Almeida avoided creating self-portraits. Rather, "My work is my body, my body is my work." "I am the canvas." Her work has been described as "halfway between a performance (capturing an instant), and body art (the body itself as the absolute protagonist).
In 1975, Almeida brought together three disciplines, photography, painting and drawing. The drawing was represented by the horsehair threads; painting in three colors – blue or red sometimes black; photography serves as a meta-narrative. The broad range of her work and experimentation includes "design to cinema, from paintings to comics, from photography to sculpture, from architecture to performance." Almeida's work is shown in the Tate Modern in London, the Museum of Art in New York, the Museu d'art Contemporary de Barcelona, and also in her home town in Lisbon. 
- Galeria Buchholz, Lisbon (1967)[better source needed]
- Venice Biennial (1982)
- Centro Galego de Arte Contemporanea, Santiago de Compostela (2000)[better source needed]
- Sydney Biennial (2004)
- The Drawing Centre, New York (2004)[better source needed]
- Venice Biennial (2005)
- Fundación Telefónica, Madrid (2009)[better source needed]
- Helena Almeida: Inside Me, Kettles Yard, Cambridge, UK (2009)
- Helena Almeida: My Work is My Body, My Body is My Work, Serralves Museum, Porto, Portugal (2015/2016)
- Work Is Never Finished, Art Institute of Chicago, Chicago, IL (2017).
- Helena Almeida, Inhabited Canvas, Tate Modern, London, 2018
- "In Memoriam 2018". photographydatabase.org.
- "Arte y tecnología. Colección Fotografía contemporánea. Helena almeida" (in Spanish). www.fundacion.telefonica.com. June 2003. Retrieved 14 February 2010.
- Johnson, Sam. "How Helena Almeida's Body Became Her Artwork". An Other Magazine. Retrieved 27 September 2018.
- Helen Almeida. Portugal: Xunta de Galicia. 19 March 2000. p. 181. ISBN 84-453-26686.
- Barrio, Javier Martín del (26 September 2018). "Muere la artista portuguesa Helena Almeida, que hizo lienzo de su cuerpo". El País (in Spanish). Retrieved 27 September 2018.
- Xunta, Helen Almeida. p. 180
- "Helena Almeida: la obra es ella". EL PAÍS, Edición impresa (in Spanish). Retrieved 31 March 2014.
- Xunta, Helen Almeida. p. 182
- "Helena Almeida | artnet". www.artnet.com. Retrieved 24 April 2017.
- Oliveira, Luísa Soares de. "Helena Almeida, a artista que era a sua própria obra". Público. Retrieved 27 September 2018.
- "Morreu a artista Helena Almeida, uma das mais reconhecidas do século XX". Observador (in Portuguese). Retrieved 27 September 2018.
- Genzlinger, Neil (11 October 2018). "Helena Almeida, Experimental Portuguese Artist, Dies at 84". The New York Times. ISSN 0362-4331. Retrieved 27 April 2019 – via NYTimes.com.
- "Helena Almeida: My work is my body, my body is my work". Serralves Foundation.
- "Art Gallery of New South Wales - Archive: Biennale of Sydney 2004". archive.artgallery.nsw.gov.au. Retrieved 27 April 2019.
- "Helena Almeida: Inside Me – Events". Kettle's Yard. Retrieved 27 April 2019.
- Seara.com. "Fundação de Serralves". Serralves. Retrieved 27 April 2019.
- "Helena Almeida: Work is never finished". The Art Institute of Chicago. Retrieved 27 April 2019.
- Tate. "Helena Almeida: until 4 November 2018 – Display at Tate Modern". Tate. Retrieved 27 September 2018.
- "A Life On Canvas: Helena Almeida, 1934–2018". The Quietus. Retrieved 27 April 2019.