LX-Lemmatizer is a freely available online service for fully-fledged lemmatization of Portuguese verbs. It was developed and is maintained at University of Lisbon by the NLX-Natural Language and Speech Group of the Department of Informatics.

LX-Lemmatizer takes a Portuguese verb form and delivers all the corresponding lemmata (infinitive forms) together with the inflectional feature values. Lemmata that are less likely, but still orthographically possible, are grouped together in a last section under the header "Other possible lemmata". At the date of its inception (November 2005), it is the first freely available online service for fully-fledged Portuguese verb lemmatization, including the full range of pronominal conjugation forms. It thus handles:
- Pronominal conjugation
- Compound tenses
- Double forms for past participles (regular and irregular)
- Past participle forms inflected for number and gender
- Negative imperative forms
- Courtesy forms for second person

LX-Lemmatizer handles both known verbs and unknown verbs. It thus lemmatizes neologisms (with orthographic suffix).