Holy Power is the unique ability which originates from the God of the Bible, the sole God of the Christian mythology, as he created the Angels who could also manipulate holy power like he could albeit to a lesser extent than the God of the Bible. The power manifests as a variation of a unique form of Light Magic, being significantly stronger then ordinary light magic as it is very lethal and poisonous to any impure and dark beings such as Devils, Vampires and Youkai.
The most common application of Holy Power is to create unique light-based weapons, which can be used offensively and can kill most lower ranked evil creatures such as Devils instantly. A number of high-ranking Angels are capable of developing holy abilities unique to themselves, such as the Seraph Uriel developing Holy Fire by holy power and fire abilities together. The Carde Baraqiel possesses the unique ability of Holy Lightning, which he created by combining holy power and lightning abilities together. His daughter; Akeno Himejima, also inherited the ability.
Due to being reincarnated as Angels, the members of the Brave Saints can also utilize holy power to various effects, such as Jessica Lagerkvist; who uses holy power to create a barrier to block attacks or Ryuu Heikan, a skilled Chinese martial artist who incorporates holy power in his physical strikes as the core of his fighting style.
The Fallen Angels, despite the fact that they were cast out of Heaven for teaching humans about Heaven's knowledge after being seduced and sleeping with human women, still maintain their ability to use holy power as the developed their own unique system of magic which is separate from the original magic system of the angels.
While originally it is only seemed possible for God of the Bible and His creations to utilize holy power, it is revealed that a dedicated believer who regulary trains his body and has a just heart, they can gain the ability to utilize holy power to a degree, as Vasco Strada was able to train himself to use holy power and developed his Holy Fist ability. 
List of Holy Powers
- Light Novel Volume 24, Life.5 The Death God and the Hyoudou Family’s Breast Technique
|High School DxD|
|Abilities||Sacred Gear • Demonic Power • Holy Power • Magic • Senjutsu (Kasha) • Youjutsu • Touki • Fox Fire • Fire Breath • Outrage|
|Abilities by Species|
|Human||Sacred Gear • Magic|
|Dragon||Fire Breath • Outrage|
|Nekomata||Senjutsu (Kasha) • Youjutsu|
|High School DxD|
|Holy Powers||Light Weapon • Holy Lightning • Holy Fire • Holy Fist • Five Card|
|Holy Powers Category|
|Elemental Holy Powers||Holy Lightning • Holy Fire|
|Other Holy Powers||Light Weapon • Holy Fist|
|Brave Saints Powers||Five Card|