Quoting R.J.B. Bosworth’s Mussolini’s Italy: Life under the Fascist Dictatorship, 1915–1945, chapter 9:

Most of the more ostentatious measures in favour of demographic growth were not instituted until after 1933, that is, until after Fascist Italy was being influenced by developments occurring far more quickly and thoroughly in [the Third Reich] (although Scandinavian social democracies were also busy intruding the state into the functioning of the family and into eugenics — more than 60,000 sterilizations were carried out in Sweden in the years after 1935).⁷⁷

Italian authorities were generally suspicious about this Northern European (and North American) confidence in a ‘scientific’ control of births, another reason why Italian racism, when it began to flourish openly during the later 1930s, usually took pains to be spiritual and ‘voluntarist’ rather than material and ‘scientific’. Eugenics was not a science with many paladins in Italy.

David Swanson’s Leaving World War II Behind, chapter 4:

It took Nazism to give eugenics a bad name in the United States, but neither [German Fascism] nor the prosecution of its members for crimes including forced sterilization ended such practices in the United States, where over 60,000 people were forcibly sterilized up through 1963, a third of them in California.

You may be wondering how many people Fascist Italy sterilized. It may be hard to believe, but it is quite possible that the number was as low as zero. The reason for this is that Rome was eager to please the Catholic Church, which opposed sterilization. (Yes, massacring socialists and Africans was acceptable, but apparently sterilization was a step too far.) Francesco Cassata’s Building a New Man: Eugenics, Racial Sciences and Genetics in Twentieth Century Italy, page 139:

Undoubtedly, the institutional, ideological and political compromise between the fascist régime and the Catholic Church—sanctioned in 1929 by the signing of the Lateran Treaty—was decisive in the affirmation—in Italy as much as in the international context—of a natalist and populationist “Latin” eugenics.

The scientific community largely sided with them. Page 144:

The scientific community followed the indications of the régime, stigmatizing the [Third Reich’s] eugenic extremism as “barbaric” and “anti‐scientific” and countering German “Aryan” mysticism with “Mediterranean” and “Latin” equilibrium.³⁷ Sante de Sanctis, at the 2nd European Conference on Mental Hygiene in September 1933, defined coercive sterilization as “catastrophic” (see chapter III).

The convention in Rome of the Society of Legal Medicine (Società di Medicina Legale) welcomed the conclusions of Salvatore Ottolenghi, in Sterilizzazione del delinquente in rapporto alla medicina legale [Sterilization of criminals in relation to legal medicine], which condemned sterilization as contrary to the spirit of the new fascist penal code.³⁸

Paolo Francesco Peloso’s Psychiatry and Psychiatric Patients in Italy During World War II:

The theme of the extermination of the unproductive mentally ill, put into practice in [the Third Reich] after 1939, was also debated in Italy, but the majority of psychiatrists, beginning with Morselli, were hostile to it [2]. During the First European Meeting for Mental Hygiene in Paris (1932), the Italian delegation showed its disapproval of the ideas of the Swiss Ernst Rudin, who favored the obligatory sterilization of patients supposedly affected by hereditary illness.

During the second meeting in Rome (1933), Sante de Sanctis confirmed the Italian antisterilization position, and during the Second International Congress of Mental Hygiene in Paris (1936), Donaggio returned to the theses of Rudin, criticizing their insufficient scientific basis. His criticisms were echoed by Lionello de Lisi (1938), who said that Italian eugenics consisted of observation, study, classification, and education leading to the development of a healthy citizen and rejected the idea of sterilization, or extermination, of disabled people.

As an alternative to radical eugenics, there was a climate in Italy of intense biopolitical intervention into social and individual health and the prevention of social illnesses [3]. An example of this orientation was the constitution of the Italian League of Hygiene and Mental Prophylactics in 1924, and eugenic issues were met with a systematized alternative called human biotypology, or ortogenetica, elaborated by Nicola Pende (1890–1980). The new science of biotypology called for a reform of clinical medicine in a preventive sense such that every citizen becomes a productive cell harmonically integrated in the Mussolini state.

The Kingdom of Italy’s subtler, pronatalist eugenics was one of the divisions between Italian Fascism and German Fascism; it was common for Italian Fascists to criticize their German counterparts for pursuing eugenic policies that were too invasive:

The Italian doctor and psychologist Sante De Sanctis, together with numerous colleagues, argued against the [Third Reich’s] racial policies such as forced sterilization, and contrasted them with the supposed civilizational power of Italian notions of race (Mantovani 2004, p.305; Cassata 2011, p.133). The December 1933 edition of the journal L’Economia Italiana delivered another broadside with 26 articles by notable population policy experts all of whom aimed to dissociate themselves, sometimes vehemently, from their counterparts in Germany (Maiocchi, 1999, p.75).

(Emphasis added in all cases.)

Even though sterilisation was illegal, it remains possible (after all, a minority still liked the idea) that the Italian Fascists sterilised a few people anyway… but so far I have not found any examples.