The Aleramici (also Aleramids) were a Northern Italian princely and royal dynasty of Frankish origin. They ruled over various northwestern Italian principalities in Piedmont and Liguria from the 10th to the 17th century, as well as over the Kingdoms of Jerusalem and Thessalonica from the 12th to 13th centuries.

Considered one of the foremost crusader dynasties, the Aleramids notably extended their influence across the Eastern Mediterranean, thrice appointed as successors to the Eastern Roman Imperial throne (under the title of Caesar), without ever ensuring their effective installation. They nevertheless produced two Imperial consorts, one of which (Irene) effectively ruled over part of the Empire under the title of Augusta. Other females of the dynasty also appear as consort-regents in several European states.

The Aleramids were only later named as such by historians seeking to identify the extensive lineage derived from the Frankish Count Aleramo, proclaimed first sovereign Marquis (or Markgrave) of Western Liguria by the Emperor Otto the Great in the year 967. Further research has allowed the division of the lineage into two main branches: the senior Marquises of Savona (later surnamed del Vasto), and the junior Marquises of Monferrat. The last became extinct during the 14th century in the Empress Irene (with female succession in the House of Palaiologos-Montferrat). The senior line of Savona carried on through multiple descending branches, mainly ruling over the Marquisates of Saluzzo and Finale until the 17th century.

Broadly, their decadence in Northern Italy can be linked to the communal movement and the consecutive loss of Imperial dominance in the region in favor of Papal or Ecclesiastical rule (12th century). By the 13th century the Aleramids had lost most of their territorial sovereignty in favor of the Republic of Genoa and the Duchy of Milan. Some late exponents (mainly del Carretto) appear as vassal-lords to the Dukes of Milan and of Savoy, while others became sovereign patricians of the Republic of Genoa. Several others (mainly Lanza) relocated to the Kingdom of Sicily where they continued to exercise a notable influence. One branch (Grana) remained in service of the Holy Roman Empire until their extinction in the 18th century (with female succession in the House of Arenberg).

The Aleramids are ancestors (through female lines) of most European royal families.

The oldest known member of the lineage was the Frankish Count William (or Willelmus), first mentioned as the father of Aleramo in the year 951. He is thought to have been the same Count Wilhelmus indicated as "dilectissimi fideles" (very beloved faithful) of the Kings Hugh of Italy and Rudolph II of Burgondy in the year 924, as well as the same Frankish Count Wilhelmus who, according to the Gesta Berengarii Imperatoris, crossed the Alps at the head of 300 Frankish knights in the year 888 in aid of Guy III of Spoleto during his quest for the Iron Crown. Although it is not clear which were the specific territories that he inherited to his son, an Imperial charter of the year 967 suggests that William passed down a substantial patrimony dispersed through the Carolingian Kingdom of Italy ("tam de hereditate parentum quam de acquistu illi advenientes per diversa loca infra Italicum Regnum coniacentes").

Aleramo, who identified himself as a member of the Salic nation and follower of the Salic law ("ex Natione Vivere et Legge Salica") received from King Hugh of Italy a similar treatment as his father ("fideli nostro Aledramo Comiti"), extending his domains in the Piedmont and Western Liguria through different donations occurred between 933 and 938 (still appearing under the rank of Count). It is still undetermined who was Aleramo's first wife and mother of all three of his children, considered by Jacob of Acqui (14th century) to be a certain princess Adelasia, daughter of the Emperor Otto the Great. Acqui's fanciful story gave rise to a much extended myth regarding Aleramo's legendary origins and unproven imperial marriage (further extended in the 19th century by Giosuè Carducci's "Cavalry and Humanism"). Aleramo's second marriage nonetheless proves his insertion amongst the Anscarids, one of Medieval Europe's most prestigious royal dynasties. Shortly after the ascent of Berengar II to the throne of Italy, Aleramo married the princess Gerberga, the King's daughter. In the year 961, Gerberga is mentioned as stepmother ("maternia") to Aleramo's children, themselves styled stepchildren ("filiastri"), and thus known to have proceeded from his previous marriage. In the same charter Aleramo is first mentioned as Marquis (“Aledramus Marchio, filius Guilielmi Comitis, et Gilberga filia domini Berengarii Regis"), suggesting the importance of the marriage in the concession of his new rank. On 10 April 967 the Emperor Otto the Great issued a charter confirming Aleramo in all his domains, counties and jurisdictional courts, alongside the then princely title of Marquis, as petitioned by the Empress consort Adelaide, daughter of Rudolph II ("Aledramum Marchionem interventu ac petitione Adhelaydae nostra coniugis atque imperii nostri participis").

Since 967, the Aleramici (name later given by historians to identify the numerous branches of Aleramo's lineage) preserved their forefather's territories alongside the title of Marquis, or Margrave in the Holy Roman Empire. According to Salic Law, the Frank's fiefdoms had to be either shared or equally divided amongst male descendants, leading to the fragmentation of the Aleramid's power and their forefather's principality. As evident in the foundational charter of the Abbey of Grazzano (year 961), Aleramo's firstborn son (William II) died in youth without having produced any offspring ("quondam Gulielmo, que fuit filius noster"), while the third-born, Otto I, also died before his father but did managed to produce two boys. After Aleramo's death around the year 999, his second-born, Anselm I took his father's place as sole head of the entire Western Ligurian March. The first testimony of his succession is found in the foundational charter of the Abbey of San Quentin in Spigno (year 999) where Anselm, son of the late Aleramo, is first mentioned as Marquis alongside his wife Gisla, daughter of Albert I of Milan ("Anselmus Marchio, filius bonae memoriae Aledrami intemque Marchio, et Gisla Comitissa iugalibus, filia Adalberti similique Marchioque"). The same charter also mentions his nephews William III and Riprand, sons of his deceased brother Otto I ("Wielelmus et Riprandus germanis, fili bonae memoriae Oddoni").