A mortal sin (Latin: peccatum mortale), in Catholic theology, is a gravely sinful act, which can lead to damnation if a person does not repent of the sin before death. A sin is considered to be ''mortal'' when its quality is such that it leads to a separation of that person from God's saving grace. This type of sin should be distinguished from a venial sin that simply leads to a weakening of a person's relationship with God. Despite its gravity, a person can repent of having committed a mortal sin. Such repentance is the primary requisite for forgiveness and absolution. Teaching on absolution from serious sins has varied somewhat throughout history. The current Catholic teaching was formalized at the 16th century Council of Trent.

can you ever be forgiven for a mortal sin?
yes