William Clay, Willie Clay, Bill Clay, or Billy Clay may refer to:

Politicians

• Bill Clay (William Lacy Clay, Sr., born 1931), politician from the state of Missouri
• Lacy Clay (William Lacy Clay, Jr., born 1956), politician from the state of Missouri
• Sir William Clay, 1st Baronet (1791–1869), English merchant and MP for Tower Hamlets

Sports

• William Clay (footballer) (born 1883), footballer
• Willie Clay (born 1970), former American football player
• Billy Clay (born 1944), American football cornerback
• William Clay (cyclist) (born 1973), American track cyclist
• Bill Clay (baseball) (1874–1917), American baseball player

Others

• William Clay (industrialist), early user of the Bessemer process in Liverpool
• William Keatinge Clay (1797–1867), English cleric and antiquary
• William D. Clay Jr., special adviser to the United Nations

See also

• William Clay Ford (disambiguation)
• Clay (disambiguation)