Papers filed in Anchorage, Alaska, on Friday identified the couple by initials - but birth and wedding dates match those of the Palins.
The paperwork, said to have been filed by Todd, cited an "incompatibility of temperament" as the reason for divorce.
The Palins, both 55, married in 1988 and have five children together.
The documents mention "an incompatibility of temperament between the parties such that they find it impossible to live together as husband and wife".
They include the initials rather than full names of the two parties - SLP for Sarah Louise Palin and TMP for Todd Mitchell Palin - but identify the couple's marriage date and the birth date of their only child who is a minor, Trig Palin.
They are asking for joint custody of the child, according to the papers.
The 'hockey mom' with political stardust
A century of trailblazers in US politics
Sarah Palin was governor of Alaska from 2006 till 2009, and shot to prominence when she became Republican Senator John McCain's running mate in the 2008 presidential election.
She and Mr McCain lost the election to Barack Obama and Joe Biden.
Since then, she has - along with Mr Palin, a commercial fisherman and oil field worker - appeared in several reality TV shows; she also has a lucrative career as a public speaker and has published two best-selling books.
She championed the grassroots Republican Tea Party movement, and was also a vocal supporter of US President Donald Trump during his 2016 presidential campaign.