Stella Nyanzi, a postdoctoral research fellow at Uganda's Makerere University, was charged with cyber harassment and offensive communication today.
She denied the charges and said President Yoweri Museveni is a "dishonorable" man who has "offended the people of Uganda."
Amnesty International urged Ugandan authorities to free Nyanzi, a single mother of three.
"Arresting Nyanzi simply for criticising the president and his wife serves no legitimate purpose," Muthoni Wanyeki, Amnesty International's regional director, said in a statement.
The charge sheet said Nyanzi had referred to Museveni as "a pair of buttocks" in one of her Facebook posts.
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