The Blizzard Challenge 2008 was the fourth annual Blizzard Challenge. This year, participants were asked to build two voices from a UK English corpus and one voice from a Mandarin Chinese corpus. This is the first time that a language other than English has been included and also the first time that a large UK English corpus has been available. In addition, the English corpus contained somewhat more expressive speech than that found in corpora used in previous Blizzard Challenges.

To assist participants with limited resources or limited experience in UK-accented English or Mandarin, unaligned labels were provided for both corpora and for the test sentences. Participants could use the provided labels or create their own. An accent-specific pronunciation dictionary was also available for the English speaker.

A set of test sentences was released to participants, who were given a limited time in which to synthesise them and submit the synthetic speech. An online listening test was conducted, to evaluate naturalness, intelligibility