The Catechism in Questions & Answers

187. What appearances of the Risen One are attested in the New Testament?

The risen Jesus appeared to His disciples on several occasions. Following are some examples:
Mary of Magdala and other women were the first witnesses of the Risen One. “And as they went to tell His disciples, behold, Jesus met them, saying ‘Rejoice!’ So they came and held Him by the feet and worshipped Him” (Matthew 28: 9).
Though unrecognised by them at first, the Risen One accompanied the disciples who were travelling to the village of Emmaus. He explained the Scriptures to them and finally broke bread with them, after which they recognised Him (cf. Luke 24: 13-35).
On the evening of His resurrection Jesus appeared in the midst of His disciples. As the Risen One and Lord over death and sin He gave the Apostles authority to make the forgiveness of sins accessible to mankind: “Receive the Holy Spirit. If you forgive the sins of any, they are forgiven them; if you retain the sins of any, they are retained” (John 20: 19-23).
On another occasion the Lord appeared to some of the disciples on the Sea of Tiberias and gave Apostle Peter the commission to “tend” the “lambs and sheep of Christ”—in other words, to care for all the members of the church (Petrine Office; cf. John 21: 15-17).
The Risen Lord also showed Himself to His Apostles “by many infallible proofs, being seen by them during forty days and speaking of the things pertaining to the kingdom of God” (Acts 1: 3).
In 1 Corinthians 15: 6, Apostle Paul mentions that the risen Jesus was seen by more than five hundred brethren at once.

Forgiveness of sins: see explanation of Question 415., Questions 644. et seq. Office of Peter: see Question 457. and explanation of Question 457.

“But Mary stood outside by the tomb weeping, and as she wept she stooped down and looked into the tomb. And she saw two angels in white sitting, one at the head and the other at the feet, where the body of Jesus had lain. Then they said to her, ‘Woman, why are you weeping?’ She said to them, ‘Because they have taken away my Lord, and I do not know where they have laid Him.’ Now when she had said this, she turned around and saw Jesus standing there, and did not know that it was Jesus. Jesus said to her, ‘Woman, why are you weeping? Whom are you seeking?’ She, supposing Him to be the gardener, said to Him, ‘Sir, if You have carried Him away, tell me where You have laid Him, and I will take Him away.’ Jesus said to her, ‘Mary!’ She turned and said to Him, ‘Rabboni!’ (which is to say, Teacher).”
John 20: 11-16