Bertha (born between 863 and 868 – March 925 in Lucca) was countess of Arles by marriage to Theobald of Arles, and margravine of Tuscany by marriage to Adalbert II of Tuscany. She served as regent of Lucca and Tuscany from 915 until 916 during the minority of her son Guy of Tuscany. She was described as beautiful, spirited, and courageous, and her influence over her spouse was, coupled with ambition, attributed to have involved her husbands in many wars.
Bertha is also known for her curious correspondence to Caliph al-Muktafi in 906, in which she described herself rather grandly as "Queen of the Franks." Bertha's letter is of interest in that she appears to have little knowledge of Baghdad politics or culture, and it is for this reason that details of her correspondence were recorded by one of the Muslim chroniclers. Bertha was seeking a marriage alliance between herself and the Emir of Sicily, unaware that al-Mukfati had little influence over the Aghlabid colony in Sicily. Moreover, the letter was written in a language unfamiliar to the Caliph's translators, and the accompanying gifts (among them a multicoloured woollen coat) which no doubt indicated largesse on Bertha's part, were unlikely to have impressed al-Muktafi beyond their novelty value.
Bertha died on 8 March 925 in Lucca.
Bertha and Theobald of Arles had four children:
Bertha and Adalbert II of Tuscany had three children: