Division: None
Age: 16-17
Height: 5'9"
Weight: 135 lbs
Birthday: July 7
Blood Type: AO
Occupation: Hollow within the conscience of Ichigo.

Hollow Ichigo (Horo Ichigo), more properly called The Hollow within Ichigo's conscience, Ichigo no naimen no Horō or White Ichigo (Shiro Ichigo), is a powerful entity that was created when Ichigo Kurosaki, a Shinigami, developed a Hollow inside his soul (during his near Hollowfication as a Plus), a commonality among the Visored. 

Among the series' most prominent antagonists, Hollow Ichigo is the longest-running villain in Bleach history, randomly appearing in almost every single story arc, including the anime-only Bount, New Captain and Zanpakutō Unknown Tales arcs. Since then, his darkly presence has been felt whenever Ichigo dons his inner Hollow's mask, and although the Hollow was defeated, he has made his return.

Appearance

Hollow Ichigo as he first appears in the anime.

His overall appearance is practically the same as Ichigo's; they look identical, only with his color scheme the opposite of Ichigo's. He is a fairly tall and lean-built being with pure white skin and hair. His eyes consists of black pupils, yellow irises and black sclera. He also has black nails. While Ichigo wears a black standard Shinigami Shihakusho, his Hollow self wears a white Shihakusho uniform with a black cloth belt. When he made his appearance in the Fake Karakura Town arc, he still wore the white Shihakusho in Bankai, although now, he dons the mask and horns of Ichigo's 2nd full hollow form.

Born from a Hollowfication process, Hollow Ichigo represents the dark side of Ichigo's soul. He has stated himself to present Ichigo's purest instincts.  As he resides within Ichigo's soul, he has become a manifestation of Ichigo's very spiritual power, meaning Ichigo's Shinigami powers also draw strength from him. 

He also has his own version of Zangetsu, Ichigo's Zanpakutō: In contrast to Ichigo's black cleaver with a silver edge wrapped in white cloths, his own Zangetsu is silver with a black edge and black wrapping cloths.

Personality

Hollow Ichigo's most distinguishing features are his maniacal laughter and psychotic grins. He is brutal, arrogant, disrespectful, and sadistic. Hollow Ichigo has no name, and his only reason for existence is to take over Ichigo's power and body to use it to kill everything and anything he sees. He taunts Ichigo as being a weak and unsuitable counterpart of himself, though he relishes the idea of taking Ichigo's powers for himself. He battles like a berserker, unlike Ichigo, ignoring injuries and overpowering his enemies with brute strength and force. He also protects Ichigo's body when he is about to die, because if Ichigo died, he would too. He also seems to respect Zangetsu's spirit to a certain extent.

Hollow Ichigo has declared that Ichigo is the "king" of the inner world and he is the "horse." Hollow Ichigo wishes to "take the crown" from Ichigo so he can have control over the body and become the dominant personality. After his loss, he states he's willing to allow Ichigo to keep the crown for now, but once Ichigo "screws up again," he declared he'd make his move again.

When he's merged with Tensa Zangetsu however, much of the Zanpakutō spirit's personality seems to be in effect, making the Inner Hollow much more calm, though he is prone to occasional outbursts similar to Hollow Ichigo. He even states that he wishes to protect Ichigo, contrary to his frequent earlier statements of wanting Ichigo's body and power for himself.

 Master Swordsmanship Specialist: In terms of fighting style, Hollow Ichigo relies mostly on his Zanpakutō and thus would be considered a swordsmanship specialist. His ingenuity in it is much greater than Ichigo's as he is able to use his skill in more versatile and effective maneuvers, such as using his Shikai as a flail, to which he has demonstrated tremendous aim and control of where and how it will strike. While Ichigo fights in a deductive and logical manner, Hollow Ichigo fights in a style more akin to a berserker, relying on instinct with little to no regard towards his own well-being.

Expert Hand-to-Hand Combatant: Drawing from Ichigo's experience, the inner Hollow is a highly capable unarmed fighter. While mostly relying on his Zanpakutō in battle, he will occasionally use unarmed attacks during the brief period his blade is swung for mid-range combat to keep from being unprotected.

Highly Perceptive Combatant: Despite his arrogant and insane demeanor, Hollow Ichigo has shown to be a very insightful and crafty fighter. While regularly mocking Ichigo, his mocking would also have deep rational knowledge behind it that would ultimately help Ichigo come to better understand himself and his powers. Hollow Ichigo's intellect has also been useful in battle. He would quickly realize mistakes in Ichigo's own battle tactics and correct them or almost instantly adapt to his opponent's battle tactics to perfectly counter them.

Vast Spiritual Power: Hollow Ichigo has a remarkable amount of energy, equal to or perhaps greater than Ichigo's. Ulquiorra, the fourth strongest among the Espada, claimed that Ichigo's reiatsu fluctuated from weak to higher than his own. 
Enhanced Strength: Hollow Ichigo has great physical strength, evidenced by him throwing Ichigo through a building. The Hollow is seen to be much more powerful than Ichigo, overpowering Ichigo very easily. His physical strength is already much greater than Ichigo's.
Enhanced Durability: He is capable of deflecting Ichigo's black Getsuga Tenshō with his unarmed left hand.

Possession: Hollow Ichigo is capable of taking over Ichigo's body and powers when Ichigo falls unconscious in a fight. In this occurrence, Ichigo's sclera blacken and his irises glow golden-yellow in combination with a Hollow mask forming on the left side of his face.

Advanced Growth Rate: Like Ichigo, Hollow Ichigo has the same astounding growth rate. He gains any power that Ichigo does, evidenced by his use of Bankai. He was even able to use the Black Getsuga Tenshō before Ichigo, despite both learning Bankai around the same time. His own Getsuga Tenshō is incomparably stronger than Ichigo's. His actual limit is unknown, as he was never in any case seen fighting with all of his strength.