Milena Markovna Kunis was born on August 14, 1983, in Chernivtsi, Ukrainian SSR in the Soviet Union. Her mother, Elvira, is a physics teacher who runs a pharmacy, and her father, Mark Kunis, is a mechanical engineer who works as a cab driver. Kunis has an elder brother named Michael. Her mother tongue and the common language within her family is Russian. She stated in 2011 that her parents had "amazing jobs", and that she "was very lucky" and the family was "not poor"; they had decided to leave the USSR because they saw "no future" there for Mila and her brother. In 1991, when she was seven years old, her family moved to Los Angeles, California, with $250. "That was all we were allowed to take with us. My parents had given up good jobs and degrees, which were not transferable. We arrived in New York on a Wednesday and by Friday morning my brother and I were at school in LA."
Kunis comes from a Jewish family and has cited antisemitism in the former Soviet Union as one of several reasons for her family's move to the United States. She has stated that her parents "raised [her] Jewish as much as they could", although religion was suppressed in the Soviet Union. On her second day in Los Angeles, Kunis was enrolled at Rosewood Elementary School, not knowing a word of English. She later recalled: "I blocked out second grade completely. I have no recollection of it. I always talk to my mom and my grandma about it. It was because I cried every day. I didn't understand the culture. I didn't understand the people. I didn't understand the language. My first sentence of my essay to get into college was like, 'Imagine being blind and deaf at age seven.' And that's kind of what it felt like moving to the States."
In Los Angeles, she attended Hubert Howe Bancroft Middle School. She used an on-set tutor for most of her high school years while filming That '70s Show. She briefly attended Los Angeles Center for Enriched Studies (LACES), but when that school proved to be insufficiently flexible about her acting commitments, she transferred to Fairfax High School, from which she graduated in 2001. She briefly attended UCLA and Loyola Marymount University in Los Angeles.