Maad a Sinig Maysa Wali Jaxateh Manneh (Serer proper : Maysa Waali Maane, many variations : Maysa Waaly Dione, Maïssa Wali Dione, Maysa Wali Jon, Maissa Waly Mané, etc.) was a king described in the oral tradition of the Serer pre-colonial Kingdom of Sine and the first of the Guelowar maternal dynasty to rule in Serer country. He reigned as Maad a Sinig (king of Sine) from c. 1350 to 1370.

In Serer oral tradition, Maysa Wali was a member of the Guelowar family who had escaped Kaabu with some members of his family after their defeat at the Battle of Troubang (1335) by the powerful Ñaanco maternal dynasty of Kaabu. Oral history describes this as a dynastic war between the two powerful royal houses of Kaabu, the House of Guelowar and the House of Ñaanco. Many members of the Guelowar family were massacred in that battle. After their defeat, those members of the Guelowar who had survived the massacre headed to the Serer pre-colonial Kingdom of Sine where they were granted asylum by the Serer nobility – the Great Council of Lamanes.

In reporting this tradition, Henry Gravrand did not notice that this is actually a description of the 1867 (or 1865) Battle of Kansala although the departure of the Guelowar can probably be explained by a war or a conflict of succession. Whatever the reason, they apparently left Kaabu around 1335.

After serving this Council for fifteen years as legal advisor, Maysa Wali gained the trust and confidence of the Council and the Serer people of Sine, and was nominated, elected and crowned king of Sine. As a result of his election, Maysa Wali became the first Guelowar to be appointed Maad a Sinig. His sisters and nieces who had escaped Kaabu with him were given in marriage to the Serer nobility, thereby sealing the union between Serer-Guelowar. As a result of these royal marriages, the old Serer paternal dynasties survived but the Wagadou maternal dynasty (Bagadou in Serer language), collapsed.

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