Are there any tools to convert markdown to Wiki text in other formats

The requirement is that I need to paste a long document in markdown format to a mediawiki site, which has no markdown extension installed. All I can find about markdown, tools or modules/libraries, are in charge of converting markdown to HTML. My question is: is there a convenient way to do the work from markdown to MediaWiki wikitext?

Try Pandoc, a universal document converter:

$ pandoc --help
pandoc [OPTIONS] [FILES]
Input formats:  docbook, haddock, html, json, latex, markdown, markdown_github,
                markdown_mmd, markdown_phpextra, markdown_strict, mediawiki,
                native, opml, rst, textile
Output formats: asciidoc, beamer, context, docbook, docx, dzslides, epub, epub3,
                fb2, html, html5, json, latex, man, markdown, markdown_github,
                markdown_mmd, markdown_phpextra, markdown_strict, mediawiki,
                native, odt, opendocument, opml, org, pdf*, plain, revealjs,
                rst, rtf, s5, slideous, slidy, texinfo, textile

It's available for virtually every platform.

Pandoc has a web tool for this.