Sigrid Undset was a Norwegian author (1882-1949) who won the Nobel Prize in 1928 for the historical, three-part novel Kristin Lavransdatter. Actually born in Kalundborg, Denmark, she attended university in Oslo, Norway (then Christiana). She would live there for most of the rest of her life, except during 1940-1945 when she resided in the United States (due to the German occupation of Norway). She converted to Roman Catholicism in 1924. Her writing before this period was almost entirely historical fiction, including The Master of Hestviken. After her divorce in 1925 from artist A. C. Svarstad, her works became more modern and also moralistic. Some of these later works are Madame Dorothea (1939) and The Faithful Wife (1936). She also wrote an autobiography in 1934 entitled The Longest Years.

Some random facts:
Kristin Lavransdatter is Connie Willis's favorite novel.
Although her works won the Nobel Prize, you will probably not find them in your local Barnes and Noble (although Penguin Classics does have a nicely translated and footnoted version of the Kristin Lavransdatter trilogy).
The only picture of her that I was able to find shows her wearing this amazing Princess Leia style cinnamon bun hairdo.

Here is the text of her Nobel Prize Acceptance Speech. Although she doesn't really say anything groundbreaking, I thought it was interesting to read...:

The preceding speakers have far better expressed our gratitude for the Prizes awarded to us than I could have done, and I subscribe to their words. I write more readily than I speak and I am especially reluctant to talk about myself. Instead, I wish to offer a salute to Sweden. Before I left for Sweden, a party was given for me - that is to say, not strictly speaking for me but because I was going to leave for Sweden - and everybody, the President of the Council of Ministers of Norway as well as my personal friends, asked me to give regards to Sweden. After all, the people of our peninsula form a distinct part of the world. Our forests and our mountains run into each other and our rivers carry their waters from one country to the other. Our houses in Norway resemble those in Sweden. God be praised! We have always lived in a great number of small, private dwellings spread all over our countries. Modern technology has not yet completely intruded on the humanity of the North.

But what I wished to say here is that I have been asked to give regards to Sweden, the country we think of with joy, and to Stockholm, which we Norwegians consider the most beautiful city in the world.