Johanne (Hanne) Ane Margrethe Nielsen (née Jacobsdatter, 11 September 1829 – 15 June 1903)[1] was a Danish farmer who may have invented Havarti cheese.

She was denied membership of the Royal Danish Agricultural Society although she had sought the assistance of dairy scientist Thomas Segelcke.

[2] Although Nielsen's attempts at selling butter and milk were successful from the beginning, she was not happy with the final products and decided to educate herself on better methods.

She studied subjects relating to dairy produce and traveled to Norway, Sweden, Switzerland and France, among others, to learn how to obtain better results.

[4] In September 1902, it was reported that all of the then-current dairy instructors in Denmark had received at least part of their training from her.

[2] She wrote press articles, held lectures, and published an 1886 Swedish manual on making butter.

[4] She asked dairy scientist Thomas Riise Segelcke [da] to let her become a member of the Agricultural Society, but he did not help her although he was a friend and visited her farm frequently.

Despite her name appearing on a membership list of the Agricultural Society from 1870 to 1871, there is no documentation of Nielsen participating in a meeting.

[3][8] The 1881 book The Channel Islands: Their People and Their Cattle said that "the products have become famous, and are found on the table of the king".