How does repentance fit into the doctrine of sola fide ("by faith alone")?

*Sola fide* (Latin for "by faith alone") is a defining doctrine of Protestantism. Wikipedia defines it as follows: > The doctrine of sola fide asserts God's pardon for guilty sinners is granted to and received through faith alone, excluding all "works". All mankind, it is asserted, is fallen and sinful, under the curse of God, and incapable of saving itself from God's wrath and curse. But God, on the basis of the life, death, and resurrection of his Son, Jesus Christ alone (solus Christus), grants sinners judicial pardon, or justification, which is received solely through faith. How does repentance fit into this doctrine? Is it possible to be unrepentant of sin (whether for some sins or all sins that one has committed) and yet still receive pardon for those sins? Is repentance considered a "work" in that it is ultimately unnecessary for justification?