Dr Denis Napthine is an Australian politician. He was elected in 1988 as the Member for Portland in the Victorian Legislative Assembly, and was Health Minister in Jeff Kennett's Liberal government through much of the 1990s.

Following the shock defeat of the Liberal Party at the 1999 election, Kennett resigned as Liberal leader, and Napthine was a surprise choice to take his place. During his term as Opposition Leader the Liberal-National coalition split, fracturing the opposition parties.

Throughout his time as Opposition Leader he was also constantly undermined by rivals within his own party room. The most visible dissident was Robert Doyle MP, Member for Malvern. Robert Doyle was supported by sources aligned to a rival group seeking control of the State Party's Administrative committee closely aligned to the Federal Treasurer, Peter Costello MP, and his University friend Michael Kroger.

Under Napthine's leadership, the Liberal Party did poorly in the polls and did not make any significant electoral inroads on the ruling Labor Government. Shortly before the 2002 state election, Doyle challenged Napthine for the leadership of the Liberal Party. Doyle won the leadership by a narrow margin, but went on to lead the party to its worst electoral defeat ever, in which Napthine nearly lost his seat.