Marc van Oostendorp (Dutch pronunciation: ['m?rk f?n 'o?st?(n)d?rp]; born 15 December 1967, Rotterdam) is a Dutch linguist and Esperantist.
From 2004 he has served as a weekly commentator on linguistics for Radio Noord-Holland.
Since 2007, he has researched phonological microvariation, dialectology and interlinguistics.
He is currently attached to the Radboud University in Nijmegen.
In Flanders and the Netherlands, van Oostendorp is known as a contributor to Genootschap Onze Taal ("Society for our language").
He collaborates with Belgian copywriter Erik Dams to produce Taalpost, a thrice-weekly e-mailed newsletter on the topic of language in general and Dutch in particular.