diff --git a/environment.yml b/environment.yml
index b75674d..ee7018e 100644
--- a/environment.yml
+++ b/environment.yml
@@ -6,6 +6,7 @@ channels:
 dependencies:
   - python
   - beautifulsoup4
+  - faiss-cpu
   - langchain
   - pytest
   - pytest-cov
diff --git a/requirements.txt b/requirements.txt
index 7ed58c0..f044e81 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,5 @@
 beautifulsoup4
+faiss-cpu  # this is an unofficial package
 langchain
 pytest
 pytest-cov
diff --git a/sphinx_rag_search_engine/embedding/tests/test_sentence_transformer.py b/sphinx_rag_search_engine/embedding/tests/test_sentence_transformer.py
index 8924e15..ece6f1f 100644
--- a/sphinx_rag_search_engine/embedding/tests/test_sentence_transformer.py
+++ b/sphinx_rag_search_engine/embedding/tests/test_sentence_transformer.py
@@ -3,7 +3,7 @@
 from sphinx_rag_search_engine.embedding import SentenceTransformer
 
 
-def test_xxx():
+def test_sentence_transformer():
     cache_folder_path = Path(__file__).parent / "data"
     model_name_or_path = "sentence-transformers/paraphrase-albert-small-v2"
 
diff --git a/sphinx_rag_search_engine/retrieval/__init__.py b/sphinx_rag_search_engine/retrieval/__init__.py
new file mode 100644
index 0000000..f4936b1
--- /dev/null
+++ b/sphinx_rag_search_engine/retrieval/__init__.py
@@ -0,0 +1,3 @@
+from ._faiss import FAISS
+
+__all__ = ["FAISS"]
diff --git a/sphinx_rag_search_engine/retrieval/_faiss.py b/sphinx_rag_search_engine/retrieval/_faiss.py
new file mode 100644
index 0000000..e05680d
--- /dev/null
+++ b/sphinx_rag_search_engine/retrieval/_faiss.py
@@ -0,0 +1,34 @@
+from numbers import Integral
+
+import faiss
+from sklearn.base import BaseEstimator
+from sklearn.utils._param_validation import HasMethods, Interval
+
+
+class FAISS(BaseEstimator):
+
+    _parameter_constraints = {
+        "embedding": [HasMethods(["fit_transform", "transform"])],
+        "top_k": [Interval(Integral, left=1, right=None, closed="left")],
+    }
+
+    def __init__(self, *, embedding, top_k=1):
+        self.embedding = embedding
+        self.top_k = top_k
+
+    def fit(self, X, y=None):
+        self._validate_params()
+        self.X_fit_ = X
+        self.X_embedded_ = self.embedding.fit_transform(X)
+        # normalize vectors to compute the cosine similarity
+        faiss.normalize_L2(self.X_embedded_)
+        self.index_ = faiss.IndexFlatIP(self.X_embedded_.shape[1])
+        self.index_.add(self.X_embedded_)
+        return self
+
+    def transform(self, X):
+        X_embedded = self.embedding.transform(X)
+        # normalize vectors to compute the cosine similarity
+        faiss.normalize_L2(X_embedded)
+        _, indices = self.index_.search(X_embedded, 1)
+        return self.X_fit_[indices[:, 0]]
diff --git a/sphinx_rag_search_engine/retrieval/tests/__init__.py b/sphinx_rag_search_engine/retrieval/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/sphinx_rag_search_engine/retrieval/tests/test_faiss.py b/sphinx_rag_search_engine/retrieval/tests/test_faiss.py
new file mode 100644
index 0000000..eac1b7e
--- /dev/null
+++ b/sphinx_rag_search_engine/retrieval/tests/test_faiss.py
@@ -0,0 +1,16 @@
+from pathlib import Path
+
+from sphinx_rag_search_engine.embedding import SentenceTransformer
+from sphinx_rag_search_engine.retrieval import FAISS
+
+
+def test_xxx():
+    cache_folder_path = (
+        Path(__file__).parent.parent.parent / "embedding" / "tests" / "data"
+    )
+    model_name_or_path = "sentence-transformers/paraphrase-albert-small-v2"
+
+    embedder = SentenceTransformer(
+        model_name_or_path=model_name_or_path, cache_folder=str(cache_folder_path)
+    )
+    faiss = FAISS(embedding=embedder).fit([{"source": "hello world", "text": "hello world"}])