diff --git a/src/poli/core/exceptions.py b/src/poli/core/exceptions.py
index 38c372c4..d960033c 100644
--- a/src/poli/core/exceptions.py
+++ b/src/poli/core/exceptions.py
@@ -17,3 +17,9 @@ class FoldXNotFoundException(PoliException):
     """Exception raised when FoldX wasn't found in ~/foldx/foldx."""
 
     pass
+
+
+class ObserverNotInitializedError(PoliException):
+    """Exception raised when the observer is not initialized."""
+
+    pass
diff --git a/src/poli/core/util/observers/csv_observer.py b/src/poli/core/util/observers/csv_observer.py
new file mode 100644
index 00000000..2f39778a
--- /dev/null
+++ b/src/poli/core/util/observers/csv_observer.py
@@ -0,0 +1,114 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from pathlib import Path
+from time import time
+from uuid import uuid4
+
+import numpy as np
+
+from poli.core.black_box_information import BlackBoxInformation
+from poli.core.exceptions import ObserverNotInitializedError
+from poli.core.util.abstract_observer import AbstractObserver
+
+
+@dataclass
+class CSVObserverInitInfo:
+    """Initialization information for the CSVObserver."""
+
+    experiment_id: str
+    experiment_path: str | Path = "./poli_results"
+
+
+class CSVObserver(AbstractObserver):
+    """
+    A simple observer that logs to a CSV file, appending rows on each query.
+    """
+
+    def __init__(self):
+        self.has_been_initialized = False
+        super().__init__()
+
+    def initialize_observer(
+        self,
+        problem_setup_info: BlackBoxInformation,
+        caller_info: CSVObserverInitInfo | dict,
+        seed: int,
+    ) -> object:
+        """
+        Initializes the observer with the given information.
+
+        Parameters
+        ----------
+        black_box_info : BlackBoxInformation
+            The information about the black box.
+        caller_info : dict | CSVObserverInitInfo
+            Information used for logging. If a dictionary, it should contain the
+            keys `experiment_id` and `experiment_path`.
+        seed : int
+            The seed used for the experiment. This is only logged, not used.
+        """
+        self.info = problem_setup_info
+        self.seed = seed
+        self.unique_id = f"{uuid4()}"[:8]
+
+        if isinstance(caller_info, CSVObserverInitInfo):
+            caller_info = caller_info.__dict__
+
+        self.all_results_path = Path(
+            caller_info.get("experiment_path", "./poli_results")
+        )
+        self.experiment_path = self.all_results_path / problem_setup_info.name
+        self.experiment_path.mkdir(exist_ok=True, parents=True)
+        self._write_gitignore()
+
+        self.experiment_id = caller_info.get(
+            "experiment_id",
+            f"{int(time())}_experiment_{problem_setup_info.name}_{seed}_{self.unique_id}",
+        )
+
+        self.csv_file_path = self.experiment_path / f"{self.experiment_id}.csv"
+        self.save_header()
+        self.has_been_initialized = True
+
+    def _write_gitignore(self):
+        if not (self.all_results_path / ".gitignore").exists():
+            with open(self.all_results_path / ".gitignore", "w") as f:
+                f.write("*\n")
+
+    def _make_folder_for_experiment(self):
+        self.experiment_path.mkdir(exist_ok=True, parents=True)
+
+    def _validate_input(self, x: np.ndarray, y: np.ndarray) -> None:
+        if x.ndim != 2:
+            raise ValueError(f"x should be 2D, got {x.ndim}D instead.")
+        if y.ndim != 2:
+            raise ValueError(f"y should be 2D, got {y.ndim}D instead.")
+        if x.shape[0] != y.shape[0]:
+            raise ValueError(
+                f"x and y should have the same number of samples, got {x.shape[0]} and {y.shape[0]} respectively."
+            )
+
+    def _ensure_proper_shape(self, x: np.ndarray) -> np.ndarray:
+        if x.ndim == 1:
+            return x.reshape(-1, 1)
+        return x
+
+    def observe(self, x: np.ndarray, y: np.ndarray, context=None) -> None:
+        if not self.has_been_initialized:
+            raise ObserverNotInitializedError(
+                "The observer has not been initialized. Please call `initialize_observer` first."
+            )
+        x = self._ensure_proper_shape(x)
+        self._validate_input(x, y)
+        self.append_results(["".join(x_i) for x_i in x], [y_i for y_i in y.flatten()])
+
+    def save_header(self):
+        self._make_folder_for_experiment()
+        with open(self.csv_file_path, "w") as f:
+            f.write("x,y\n")
+
+    def append_results(self, x: list[str], y: list[float]):
+        with open(self.csv_file_path, "a") as f:
+            for x_i, y_i in zip(x, y):
+                f.write(f"{x_i},{y_i}\n")
diff --git a/src/poli/tests/observers/test_csv_observer.py b/src/poli/tests/observers/test_csv_observer.py
new file mode 100644
index 00000000..a34cbfd8
--- /dev/null
+++ b/src/poli/tests/observers/test_csv_observer.py
@@ -0,0 +1,104 @@
+import csv
+
+import numpy as np
+import pytest
+
+from poli.core.exceptions import ObserverNotInitializedError
+from poli.core.util.observers.csv_observer import CSVObserver, CSVObserverInitInfo
+from poli.repository import AlohaBlackBox
+
+
+def test_csv_observer_logs_on_aloha():
+    f = AlohaBlackBox()
+    observer = CSVObserver()
+    observer.initialize_observer(
+        f.info,
+        {
+            "experiment_id": "test_csv_observer_logs_on_aloha",
+            "experiment_path": "./poli_results",
+        },
+        seed=0,
+    )
+
+    f.set_observer(observer)
+    f(np.array([list("MIGUE")]))
+    f(np.array([list("ALOOF")]))
+    f(np.array([list("ALOHA"), list("OMAHA")]))
+
+    assert observer.csv_file_path.exists()
+
+    # Loading up the csv and checking results
+    with open(observer.csv_file_path, "r") as f:
+        reader = csv.reader(f)
+        results = list(reader)
+
+    assert results[0] == ["x", "y"]
+    assert results[1][0] == "MIGUE" and float(results[1][1]) == 0.0
+    assert results[2][0] == "ALOOF" and float(results[2][1]) == 3.0
+    assert results[3][0] == "ALOHA" and float(results[3][1]) == 5.0
+    assert results[4][0] == "OMAHA" and float(results[4][1]) == 2.0
+
+
+def test_csv_observer_works_with_incomplete_caller_info():
+    f = AlohaBlackBox()
+    observer = CSVObserver()
+    observer.initialize_observer(
+        f.info,
+        {},
+        seed=0,
+    )
+
+    f.set_observer(observer)
+    f(np.array([list("MIGUE")]))
+    f(np.array([list("ALOOF")]))
+    f(np.array([list("ALOHA"), list("OMAHA")]))
+
+    assert observer.csv_file_path.exists()
+
+    # Loading up the csv and checking results
+    with open(observer.csv_file_path, "r") as f:
+        reader = csv.reader(f)
+        results = list(reader)
+
+    assert results[0] == ["x", "y"]
+    assert results[1][0] == "MIGUE" and float(results[1][1]) == 0.0
+    assert results[2][0] == "ALOOF" and float(results[2][1]) == 3.0
+    assert results[3][0] == "ALOHA" and float(results[3][1]) == 5.0
+    assert results[4][0] == "OMAHA" and float(results[4][1]) == 2.0
+
+
+def test_observer_without_initialization():
+    f = AlohaBlackBox()
+    observer = CSVObserver()
+
+    f.set_observer(observer)
+
+    with pytest.raises(ObserverNotInitializedError):
+        f(np.array([list("MIGUE")]))
+
+
+def test_works_with_csv_init_object():
+    f = AlohaBlackBox()
+    observer = CSVObserver()
+    observer.initialize_observer(
+        f.info,
+        CSVObserverInitInfo(
+            experiment_id="test_csv_observer_logs_on_aloha",
+            experiment_path="./poli_results",
+        ),
+        seed=0,
+    )
+    f.set_observer(observer)
+    f(np.array([list("MIGUE")]))
+    f(np.array([list("ALOOF")]))
+    f(np.array([list("ALOHA"), list("OMAHA")]))
+    assert observer.csv_file_path.exists()
+    # Loading up the csv and checking results
+    with open(observer.csv_file_path, "r") as f:
+        reader = csv.reader(f)
+        results = list(reader)
+    assert results[0] == ["x", "y"]
+    assert results[1][0] == "MIGUE" and float(results[1][1]) == 0.0
+    assert results[2][0] == "ALOOF" and float(results[2][1]) == 3.0
+    assert results[3][0] == "ALOHA" and float(results[3][1]) == 5.0
+    assert results[4][0] == "OMAHA" and float(results[4][1]) == 2.0