William Hardcastle may refer to:

• Bill Hardcastle (1874–1944), New Zealand and Australian national representative rugby union and rugby league player
• William Hardcastle (broadcaster) (1918–1975), British journalist and radio news presenter
• William Hardcastle (football chairman), see 1912–13 Huddersfield Town F.C. season

• 2004-05 Ipswich Town F.C. season
• 2004-05 Iranian Basketball Super League
• 2004-05 Iranian Futsal Super League
• 2004-05 Iranian Volleyball Super League
• 2004-05 Iran Pro League
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• 2004-05 Israeli Hockey League season
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• 2004-05 Latvian Hockey League season
• 2004-05 Lebanese Premier League
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• 2004-05 Lithuanian Hockey League season
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• 2004-05 Logan Cup
• 2004-05 Louisville Cardinals men's basketball team
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• 2004-05 Memphis Grizzlies season
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• 2004-05 Millwall F.C. season
• 2004-05 Milwaukee Bucks season