The England striker followed up his treble over Burnley on Saturday by heading in a Christian Eriksen free-kick in the 22nd minute for his 37th league goal of 2017, beating Alan Shearer's 22-year-old record for the most goals in England's top flight in a calendar year.
Kane then overtook Messi as the top scorer of the year in Europe for club and country by tapping in Son Heung-min's low cross in the 39th minute. In the second half Kane scored his side's fifth goal of the game to become the first player to hit six Premier League hat-tricks in one year.
Impressive strikes from Dele Alli and Son had further stretched Tottenham's lead in the second half, while Sofiane Boufal hit back for struggling Southampton to make it 4-1 before the relentless Kane struck once again with a classy chipped finish over Fraser Forster in the 67th minute.
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Substitute Dusan Tadic got another consolation goal for the visitors, who are 13th on 19 points and only three clear of the relegation zone. Spurs provisionally climbed up to fourth on 37 points, although Liverpool could overtake them again if they beat Swansea City later on Tuesday.
(Reporting by Richard Martin; Editing by Christian Radnedge)
