Historically, the interrelationships of titanosaurs have been highly unstable and varied between different analyses. Despite this, Patagotitan has been consistently found as being grouped with Argentinosaurus and Puertasaurus in analyses including the three titanosaurs, with either one being its closest relative. In 2018, Bernardo González Riga and colleagues found Patagotitan to form a polytomy with Puertasaurus and Notocolossus, with Argentinosaurus being closest to this group; unlike Carballido and colleagues, however, they recovered the Lognkosauria within the Lithostrotia. In 2019, González Riga and colleagues recovered the same arrangement, and they named the group formed by the Lognkosauria and the Rinconsauria as Colossosauria. Also in 2019, Philip Mannion and colleagues found the group of Patagotitan, Puertasaurus, and Notocolossus in a polytomy with other titanosaurs, which included Argentinosaurus, Futalognkosaurus, Mendozasaurus, and others depending on the exclusion of some other titanosaurs from the analysis; this exclusion also affected whether Lognkosauria was inside Lithostrotia. In 2020, Carballido and colleagues found again that Patagotitan grouped with Argentinosaurus, with their grouping being in a polytomy with Puertasaurus and Drusilasaura, and Lognkosauria being outside Lithostrotia; Federico Agnolin and colleagues found a similar arrangement in 2023. In 2021, Otero and colleagues recovered the same arrangement. Also in 2021, Pablo Gallina and colleagues recovered a similar arrangement, except with Ninjatitan possibly being closer to Patagotitan and Argentinosaurus than Puertasaurus. In 2023, Agustín Pérez Moreno and colleagues performed an analysis based on that of Gallina and colleagues, and found a similar arrangement except with Ninjatitan closer to the Rinconsauria.
