In Catholic theology, the "father of lies" is a reference to Satan

In Catholic theology, the "father of lies" is a reference to Satan, also known as the devil. The title is derived from the Bible, in which Satan is described as being "the father of lies" (John 8:44). This is because Satan is the source of all deception and falsehood. He is constantly trying to lead people astray from God and His truth.
The Catechism of the Catholic Church describes Satan as "a fallen angel, who rebelled against God and was cast out of heaven" (CCC 391). He is "the enemy of God and of man" (CCC 392). Satan is "the tempter" (CCC 395), who "seeks to divert man from God and his plan" (CCC 398).
The Catholic Church teaches that Satan can be defeated by the power of God. Through faith, prayer, and good works, we can resist Satan's temptations and live in accordance with God's will.
Here are some other passages from the Bible that refer to Satan as the "father of lies":
"You are of your father the devil, and your will is to do your father's desires. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies." (John 8:44)
"Be alert and of sober mind. Your enemy the devil prowls around like a roaring lion looking for someone to devour." (1 Peter 5:8)
"Resist the devil, and he will flee from you." (James 4:7)
We can pray to God for protection from Satan and his lies. We can also ask for the help of the Holy Spirit to discern the truth and to resist temptation.