Mazie Hirono was born on November 3, 1947, in Fukushima Prefecture, Japan to Laura Chie Satō, a Japanese American, and Hirono Matabe, a Japanese veteran of World War II. Mazie’s maternal grandfather, Hiroshi Satō, immigrated to Hawaii to work on a sugar plantation at the age of 16; her grandmother, Tari Shinoki, immigrated to Hawaii as a picture bride. After finding plantation work difficult, the couple opened a bathhouse on River Street in Honolulu in 1928. The couple had a daughter, Laura Chie, in 1924, and a son, Akira.

Mazie’s father, Matabe, was a compulsive gambler and alcoholic who pawned even his wife’s possessions for gambling money. Treated “like a slave” by her in-laws, Mazie’s mother finally left the abusive marriage in 1951. Laura later recounted her point of decision: “My brother sent money to buy a school uniform for my son. My husband took the money, went to town and never came back home. It was getting closer to the start of school, so I went to look for him. I found out he had ordered an overcoat for himself with the money. He didn’t need an overcoat in the spring. That’s when I made up my mind to leave.” After telling her in-laws she was going to take her children to school in her hometown, Laura left the house, never to return. Selling her clothes to pay the rail fare, she and the children moved back to her parents’ home. Laura said, “My husband never came around once; my parents were supportive and took all of us in. My mother gave us money. I guess it all boils down to love.”

The Satō-Hirono family decided to return to Hawaii, but under the U.S. quota system Tari and Hiroshi, as Japanese Americans without citizenship or professional status, could not go with Laura, an American citizen. Thus the family was separated, with three-year-old Wayne staying behind with his grandparents and Laura returning to Honolulu on her own with Mazie and Roy in March 1955. After two years of hard work, she brought her parents and youngest son to Hawaii in 1957. “She determined that she had to get away [from her husband]…she wanted to put thousands of miles between them”, Hirono said of her mother. “That took a lot of courage. I always tell my mom there is nothing I can do—hard as it is to be in politics…harder than what she did.”

Raised in Honolulu, Hirono became a naturalized U.S. citizen in 1959, the year Hawaii became a state. She attended Kaʻahumanu Elementary and Koko Head Elementary Schools. She graduated from Kaimuki High School, which at the time of her attendance had a predominantly Japanese American student body. Hirono then enrolled at the University of Hawaii at Mānoa, graduating Phi Beta Kappa with a B.A. in psychology in 1970. She left Hawaii to attend Georgetown University Law Center, where she obtained her J.D. degree in 1978. Hirono then returned to Honolulu, where she practiced law.

Hirono never saw her father again, and he has since died. Laura became a newspaper proofreader in 1961 and retired from the Hawaii Newspaper Agency in 1986; Roy became a Hawaiian Electric supervisor. Wayne drowned in 1978, aged 26. Mazie’s grandfather Hiroshi died in 1989, and her grandmother Tari died in 2000 at age 99.

In 1980 Hirono was elected to Hawaii’s 12th House district in a multi-member district with Democratic State Representative David Hagino. Hawaii eliminated multi-member districts, and after redistricting she ran for Hawaii’s 20th House district and won. After redistricting again in 1984, she ran for the newly redrawn Hawaii’s 32nd House district and won. In 1992, after redistricting, she ran in the newly redrawn Hawaii’s 22nd House district. She won the three-candidate Democratic primary with 91% of the vote. She won the general election and served only one term in the 22nd district before retiring in 1994 to run for statewide office.

From 1980 to 1994 Hirono served in the Hawaii House of Representatives, passing more than 120 laws. She was honored by a coalition of leaseholders as Legislator of the Year in 1984.

From 1987 to 1992 she was Chair of the Consumer Protection and Commerce Committee.

In 1994 Hirono joined the ticket of incumbent Lieutenant Governor Benjamin J. Cayetano and was elected to a historic administration led by the first Filipino American governor and first Japanese immigrant lieutenant governor. During her tenure as lieutenant governor, she was president of the National Commission on Teaching, America’s Future, and the Hawaii Policy Group. She also spearheaded the first-in-the-nation comprehensive Pre-Plus program, a precursor to universal preschool education in the United States.

Hirono ran for reelection in 1998. She was challenged in the primary by Nancy L. Cook and defeated her, 89%–11%. In the general election Hirono defeated Republican State Senator Stan Koki 50%–49%, a difference of 5,254 votes.

In 2008 Hirono was named the national preschool advocacy organization Pre-K Now’s “Pre-K Champion” for her efforts on behalf of pre-kindergarten legislation.

Hirono co-sponsored and signed the Prevention First Act of 2007. The act aimed to increase public access to contraception and government funding to support the use of contraception. It places an emphasis on informing and protecting women from unintended pregnancy. On May 4, 2011, Hirono voted against the No Taxpayer Funding for Abortion Act, which would have prohibited federal health care programs from covering abortion costs, with exceptions for life-threatening cases.

In July 2011 Hirono voted for the Access to Birth Control Act, which mandates that pharmacies provide birth control to customers without undue delay. The ABP Act also ensures that customers seeking birth control can obtain it without being submitted to unwanted harassment or breaches in patient confidentiality. EMILY’s List, a Democratic pro-choice action committee, pledged support to Hirono for her history of supporting contraceptive and abortion policies during her term. Its endorsement helped Hirono in her 2012 senatorial race, contributing $129,714 to her campaign.

On May 19, 2011, Hirono announced her candidacy for the U.S. Senate seat left open by Daniel Akaka, who was retiring at the end of his term in 2012. She won the Democratic primary election on August 11, 2012. Hirono was endorsed as one of Democracy for America’s Dean Dozen. The Republican nominee was former Hawaii Governor Linda Lingle. Hirono won the general election on November 6, 2012, with 63% of the vote. She is the first female senator from Hawaii, as well as the first Asian-born immigrant to be elected to the U.S. Senate. She was a part of the first completely non-Christian Congressional delegation from the state, which continued until the election of Mark Takai (an Episcopalian) in 2014 as Representative of Hawaii’s 1st congressional district.

In the 2012 campaign Hirono raised $5.2 million, with approximately 52% of that from large corporations. Lingle raised $5.5 million, with 74% from large corporations. Hirono spent $5 million and Lingle $4.8 million.

On December 12, 2012, the Senate Democratic Steering Committee announced that Hirono would serve on the Senate Judiciary Committee, giving her influence on matters ranging from approving nominations of federal judges to setting criminal-justice policy.

In 2016, she participated in the Chris Murphy gun control filibuster. Hirono expressed disappointment when the Democrat-proposed Feinstein Amendment (banning the sale of firearms to individuals on the terrorist watchlist) and the Republican-backed background check expansion and alert system (regarding guns being sold to terrorist watchlist suspects) both failed to pass the Senate.

On July 28, 2017, two months after undergoing surgery for stage-four kidney cancer, Hirono spoke on the Senate floor and voted against the so-called “skinny repeal” of the Affordable Care Act (Obamacare). MSNBC reporter Kyle Griffin filmed Hirono’s speech and posted it on Twitter.

Hirono announced in May 2017 that she had been diagnosed with stage 4 kidney cancer, which had spread to her seventh rib. The cancer was discovered in a chest X-ray in April before minor eye surgery. Hirono’s right kidney was removed on May 17, 2017, with a Cyberknife procedure to treat the rib lesion. She returned to the Senate on May 22, 2017, and was reelected to a second term in 2018.

On November 6, 2018, Hirono was reelected with 71.2% of the vote, defeating Republican Ron Curtis.

During the Brett Kavanaugh Supreme Court nomination hearings in September 2018, Hirono became an outspoken defender of Christine Blasey Ford after Ford accused Kavanaugh of sexual assault, telling men to “shut up and step up. Do the right thing for a change.”

In January 2019, during the 2018–19 United States federal government shutdown, Hirono was one of 34 senators to sign a letter to Commissioner of Food and Drugs Scott Gottlieb recognizing the efforts of the FDA to address the effect of the government shutdown on the public health and employees while expressing alarm “that the continued shutdown will result in increasingly harmful effects on the agency’s employees and the safety and security of the nation’s food and medical products.” Gottlieb said additional staff might be called in as needed.

In April 2019, Hirono was one of 41 senators to sign a bipartisan letter to the housing subcommittee praising the United States Department of Housing and Urban Development’s Section 4 Capacity Building program as authorizing “HUD to partner with national nonprofit community development organizations to provide education, training, and financial support to local community development corporations (CDCs) across the country” and expressing disappointment that Trump’s budget “has slated this program for elimination after decades of successful economic and community development.” The senators wrote of their hope that the subcommittee would support continued funding for Section 4 in Fiscal Year 2020.

In April 2019, Hirono was one of seven senators to sponsor the Digital Equity Act of 2019, legislation establishing a $120 million grant program that would fund the creation and implementation of “comprehensive digital equity plans” in every state and a $120 million grant program to support projects developed by individuals and groups. The bill also gave the National Telecommunications and Information Administration (NTIA) the role of evaluating and providing guidance for digital equity projects.