Lettres de creance refers to a document, typically issued by a country's government, which grants authority and legitimacy to an ambassador, diplomat, or envoy representing that nation on the international stage. Though this phrase is common in diplomatic contexts, there are several synonyms that can be used to describe these types of documents, including letters of credence, credentials, or a letter of introduction. While the wording may vary depending on the exact document and context, they all serve a similar purpose: to establish an individual's credentials and authority in order to represent their nation in diplomatic dealings with other countries.