In the run up to the next Spanish general election, various organisations carry out opinion polling to gauge voting intention in Spain during the term of the 15th Cortes Generales. Results of such polls are displayed in this article. The date range for these opinion polls is from the previous general election, held on 23 July 2023, to the present day.

Voting intention estimates refer mainly to a hypothetical Congress of Deputies election. Polls are listed in reverse chronological order, showing the most recent first and using the dates when the survey fieldwork was done, as opposed to the date of publication. Where the fieldwork dates are unknown, the date of publication is given instead. The highest percentage figure in each polling survey is displayed with its background shaded in the leading party's colour. If a tie ensues, this is applied to the figures with the highest percentages. The "Lead" columns on the right shows the percentage-point difference between the parties with the highest percentages in a poll.