The use of native flora by Apis mellifera L. in Chile has been demonstrated in many studies; however, certain species that are viewed as weeds contribute extensively to the floral composition of honey. A total of 92 honey samples from the Libertador General Bernardo O'Higgins region in Chile were analyzed to determine which weeds are most important in honey production and which are most preferred by melliferous bees. Their relative contributions to the pollen fraction of each honey sample were also determined using melissopalynological tests in accordance with Chilean regulation (NCh2981.Of2005; Ministerio de Agricultura. 2006) to evaluate the botanical origins of the honey samples. Species considered weeds were classified according to their importance in Chilean crops, as proposed by Matthei (1995), based on the classification system by Holm (1979). These authors categorize weeds on a scale that ranges from "very serious", if they potentially cause significant crop loss, to "occasionally present as weeds" if they are part of the national flora. A total of 19 weeds were identified at the species level from the pollen types found, and five weeds were identified at the genus level. The weeds were classified as contributing very frequently, frequently, rarely and occasionally to honey using the methodology described by Louveaux et al. (1970) for determining the frequency with which plant species contribute to honey based on the corresponding pollen types found in honey. Overall, 74% of the weeds used by Apis mellifera were European, and 53% of the weeds had perennial life cycles. The families that contributed the most to honey production were Fabaceae, Asteraceae and Brassicaceae. The importance of species viewed as weeds in the production of Chilean honey is discussed.