Who is Holy Spirit in Quran ?

☪️Say, [O Muhammad], “The Holy Spirit [i.e., Gabriel] has brought it down from your Lord in truth to make firm those who believe and as guidance and good tidings to the Muslims. ( An-Nahl 16:102 )

☪️The Trustworthy Spirit [i.e., Gabriel] has brought it down. ( Quran 26:193 )

☪️Say, if someone is an enemy to Gabriel (it can by no means degrade him for) it is he who has brought it (the Qur’ān) down upon your heart by the permission of Allah, confirming what has been before it, and a guidance and good tidings to the believers, Whoever is an enemy to Allah and His Angels and His Messengers, and Jibril and Mikal, (Angle Gabriel and Michael, respectively) then surely Allah is an enemy to the disbelievers. ( Quran 2:97:98)

☪️Indeed, We gave Moses the Book, and after him We sent messengers, one following the other; and We gave clear signs to ‘Īsā, the son of Maryam (Jesus, the son of Mary), and supported him with the Holy Spirit. Then, how is it that every time a prophet came to you with what does not meet your desires, you grew arrogant? So, you gave the lie to a group (of the messengers) and killed others. ( Quran 2:87)

☪️[That] indeed, the Qur’an is a word [conveyed by] a noble messenger,Who is] possessed of power and with the Owner of the Throne, secure [in position], Obeyed there [in the heavens] and trustworthy.( Quran 81:19:20)

➡️As interpreted to refer to the Archangel Gabriel.
The term Rūḥ al-Qudus is also an epithet referring to the Archangel Gabriel, who is related as the Angel of revelation and was assigned by God to reveal the Qurʼan to the prophet Muhammad and who delivered the Annunciation to Mary.

➡️In the two suras in which the Qur’an refers to the angel Gabriel, it does so by name.(Quran 2:97–98, Quran 66:4 ) However, some ahadith and parts of the Qurʼan may arguably lend support to the alternative view.

➡️It appears to be indicated by the Quran in sura Maryam, ayat 16–21, that it was the angel Gabriel who gave to Mary the tidings that she was to have a son as a virgin:

☪️Maryam 19:16-21
And mention, [O Muhammad], in the Book [the story of] Mary, when she withdrew from her family to a place toward the east.And she took, in seclusion from them, a screen. Then We sent to her Our Angel [i.e., Gabriel], and he represented himself to her as a well-proportioned man. And she took, in seclusion from them, a screen. He said, “I am only the messenger of your Lord to give you [news of] a pure boy [i.e., son].She said, “How can I have a boy while no man has touched me and I have not been unchaste?”He said, “Thus [it will be]; your Lord says, ‘It is easy for Me, and We will make him a sign to the people and a mercy from Us. And it is a matter [already] decreed.