Virgil -- Virgil serves as Dante's guide through Hell. The real Dante was a poet who lived in northern Italy during the Roman era. Virgil was regarded as the greatest Roman poet, and his classic, the Aenid which tells of the mythological journey of a group of Trojan survivors after the fall of Troy as they journey from their homeland to Italy, where they found the City of Rome.
Virgil has been condemned to Hell because he worshipped the old pagan gods, and lived before the time of Christ and so had no possibility of Redemption. The spirit of Virgil has been ordered to be Dante's guide. Throughout the journey, Virgil is a useful guide and companion to Dante but is sometimes powerless to protect Dante from the real dangers of the Inferno. Some critics regard Virgil as an allegorical representation of reason, as opposed to faith in God, and his inability to protect Dante from the dangers of Hell symbolizes the ineffectiveness of pure reason compared to belief in Christ. The choice of Virgil as a guide is significant because prior to his entry into Hell, Dante aspires to be like Virgil.
Beatrice -- Beatrice is a young woman, and Dante's true love. She is pure of heart and has been allowed to enter Heaven. Dante is distraught by her loss and at the beginning of the Inferno, he has become lost (literally and metaphorically). In the depth of his despair, Dante is contemplating suicide. Beatrice saves him by asking an angel to send Virgil to Dante and allowing Dante to make the journey through Hell, Purgatory and Heaven which corresponds to Dante's spiritual ascent from the depths of sin to redemption. Beatrice is not present in most of the Inferno, but she is Dante's personal guide through Purgatory and Heaven.
In real life, Beatrice died very young. It is unclear whether Dante really knew her well, or whether he merely used her as an allegory for spiritual love.
In addition to the main characters, Dante encountes a large number of minor mythological creatures and demons as well as souls of the damned, based on real people. Some of these encounters are very fleeting in nature, while at other times Dante stops to converse with the spirits.
Fra Alberigo was a friar and member of the Guelph political party in Florence. Alberigo had his cousin and his son killed when they were guests at a banquet hosted by Alberigo. This act of treachery earned Alberigo a place in the Ninth Circle of Hell.
Antaeus - Antaeus is a giant borrowed from Roman mythology. In the Inferno, he transports Dante and Virgil from the Eighth to the Ninth Circle of Hell.
Filippo Argenti - Another Florentine and political enemy of Dante in real life. In the Inferno, Argenti is condemned to the Fifth Circle of Hell. He is to spend eternity among the Wrathful (his sin in life) who reside in the river Styx.
Guido da Montefeltro - Another adversary of Dante in Dante's real life political career. Montefeltro was an advisor to Pope Boniface VIII (himself now residing in Hell). This corrupt man sold Papal indulgences which promised forgiveness and absolution from sins before they were even committed. In effect they served as licences to commit the offence with supposed impunity. But of course, it was just a scam for profit which led many to spiritual ruin. It is not possible to be forgiven for a sin without repentance. And it is impossible to repent of a sin before committing it. This Montefeltro's indulgences were invalid. Ironically, Montefeltro now suffers eternal torment because he did not repent.
Malacoda - Malacoda is one of the demons who reside in the Inferno. His name means evil tail" in Italian. Malacoda is a the leader of a the demons who guard a part of the Eight Circle of Hell. He gives Virgil and Dante misleading directions.
Muhammad (c. 570–632): The founder of Islam. According to Dante, he is found among "the sowers of dissension".
Pope Boniface VIII - This Pope was notoriously corrupt, and sought to increase the political power of the Papal States which were the territories in Italy ruled directly by the Pope. In placing this Pope in Hell, Dante is taking a shot at his real life political adversaries. The real Dante belonged to a political faction in Florence that opposed the temporal power of the Pope.
Phlegyas - The boatman who rows Dante and Virgil across the river Styx.
Pier della Vigna - One of the suicides that Dante encounters in Hell. Della Vigna was an advisor to Emperor Frederick II. He killed himself after he fell out of the emperor's favor. He now must spend eternity in the form of a tree.
Count Ugolino -- Another Italian political figure of Dante's era. Ugolino has been condemned to the Ninth Circle of Hell, the worst part of Hell which is reserved for traitors. In the Inferno, Ugolino is condemned to eternally eat the head of another traitor, Archbishop Ruggieri. In the real world, Ruggieri had imprisoned Ugolino and his sons, without food in order to starve them to death. Ugolino had eaten his sons.