Bill
The name Bill or Billy might refer to:

Documents
 Bill (advertisement), an announcement for an entertainment event
 Bill (law), a law proposed or enacted by legislation
 Ferengi Bill of Opportunities
 Vulcan Bill of Rights
 Bill (payment), a type of invoice for monies owed
 Bar bill
 Bill of sale
 Medical bill
 "Clean bill of health", a phrase meaning one was healthy

People
 Bill (Admiral), 23rd century Starfleet Fleet Admiral
 Bill (Borg), identity of a Borg drone, as identified by Magnus Hansen
 Billy (Carbon Creek), a resident of Carbon Creek in the 1950s
 Billy (Starfleet), an officer aboard the Enterprise NX-01

See also 
 William Claiborne, referred to as "Billy"
 William T. Riker, referred to, rarely, as "Bill" or "Billy"
 William Ross, referred to as "Bill"
 William Samuels, referred to as "Bill"
 William Telfer, referred to as "Billy"