Guglielma Pallavicini (rarely Wilhelmina; died 1358), the Lady of Thermopylae, was the last Pallavicino heir to rule in Bodonitsa. She was but an infant when she succeeded her father Albert in 1311. She shared the margraviate with her mother Maria dalle Carceri and later with her stepfather Andrea Cornaro and her own husband Bartolomeo Zaccaria.
The succession of all Latin fiefs in Greece was regulated at the time of Albert's death by the Book of the Customs of the Empire of Romania. By custom, the inheritance was split between the widow and daughter. Maria soon remarried to Andrea in order to protect the margraviate from Catalan incursions.
In 1327, Guglielma married the Genoese Zaccaria, who had been captured while repelling, alongside Andrea Cornaro, an invasion of Alfonso Fadrique of Athens. In 1334, Bartolomeo died and Guglielma married Niccolò Zorzi, a Venetian. This marriage was especially important after the death of Cornaro, for it allowed her to remain in residence on Negroponte and to reconcile her claims to the castle of Larmena with Venice's. In fact, Guglielma had contacted the Republic beseeching one of their own as a husband. Zorzi arrived in Bodonitsa in 1335.
Guglielma and Niccolò continued the annual tribute of four destriers made to the Athenian Catalans. Peace did not attend their house, however. Venice continued the dispute over Larmena and even sought the arbitration of the bailiff of Catherine II, Princess of Achaea, the legal suzerain of Euboea and Bodonitsa. The bailiff decided for Venice. This strained the marriage, with Guglielma accusing her husband of "cowardice and bias [towards Venice]." Guglielma further believed that he ignored the interests of her child by Bartolomeo, Marulla, in favour of his own offspring. Guglielma had saved a large amount of money for her daughter, but deposited in a Venetian bank. The marchioness was finally whipped into a fury by the execution of her relative Manfredo, ordered by her husband. While the execution had been legal, Guglielma stirred the people against Zorzi, who was forced to flee to Negroponte.