diff --git a/examples/seq2seq/pack_dataset.py b/examples/seq2seq/pack_dataset.py
new file mode 100644
index 0000000000..fc2e0d78b4
--- /dev/null
+++ b/examples/seq2seq/pack_dataset.py
@@ -0,0 +1,63 @@
+"""Fill examples with bitext up to max_tokens without breaking up examples.
+[['I went', 'yo fui'],
+['to the store', 'a la tienda']
+]
+=> ['I went to the store', 'yo fui a la tienda']
+"""
+
+import argparse
+from pathlib import Path
+
+from tqdm import tqdm
+
+from transformers import AutoTokenizer
+
+
+def pack_examples(tok, src_examples, tgt_examples, max_tokens=1024):
+
+    finished_src, finished_tgt = [], []
+    new_src, new_tgt = "", ""
+    sorted_examples = list(sorted(zip(src_examples, tgt_examples), key=lambda x: len(x[0])))
+
+    def is_too_big(strang):
+        return tok(strang, return_tensors="pt").input_ids.shape[1] > max_tokens
+
+    for src, tgt in tqdm(sorted_examples):
+        cand_src = new_src + " " + src
+        cand_tgt = new_tgt + " " + tgt
+        if is_too_big(cand_src) or is_too_big(cand_tgt):  # cant fit, finalize example
+            finished_src.append(new_src)
+            finished_tgt.append(new_tgt)
+            new_src, new_tgt = src, tgt
+        else:  # can fit, keep adding
+            new_src, new_tgt = cand_src, cand_tgt
+
+    return finished_src, finished_tgt
+
+
+def pack_data_dir(tok, data_dir: Path, max_tokens, save_path):
+    save_path = Path(save_path)
+    save_path.mkdir(exist_ok=True)
+    for split in ["val", "test", "train"]:
+        src_path, tgt_path = data_dir / f"{split}.source", data_dir / f"{split}.target"
+        src_docs = list(Path(src_path).open().readlines())
+        tgt_docs = list(Path(tgt_path).open().readlines())
+        src, tgt = pack_examples(tok, src_docs, tgt_docs, max_tokens)
+        print(f"packed {split} split from {len(src_docs)} examples -> {len(src)}.")
+        Path(save_path / f"{split}.source").open("w").write("\n".join(src))
+        Path(save_path / f"{split}.target").open("w").write("\n".join(tgt))
+
+
+def packer_cli():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--tok_name", type=str, help="like facebook/bart-large-cnn,t5-base, etc.")
+    parser.add_argument("--max_seq_len", type=int, default=128)
+    parser.add_argument("--data_dir", type=str)
+    parser.add_argument("--save_path", type=str)
+    args = parser.parse_args()
+    tokenizer = AutoTokenizer.from_pretrained(args.tok_name)
+    return pack_data_dir(tokenizer, Path(args.data_dir), args.max_seq_len, args.save_path)
+
+
+if __name__ == "__main__":
+    packer_cli()
diff --git a/examples/seq2seq/test_seq2seq_examples.py b/examples/seq2seq/test_seq2seq_examples.py
index 3989046e65..0a6c59ab38 100644
--- a/examples/seq2seq/test_seq2seq_examples.py
+++ b/examples/seq2seq/test_seq2seq_examples.py
@@ -16,6 +16,7 @@ from transformers.testing_utils import require_multigpu
 
 from .distillation import distill_main, evaluate_checkpoint
 from .finetune import main
+from .pack_dataset import pack_data_dir
 from .run_eval import generate_summaries_or_translations, run_generate
 from .utils import SummarizationDataset, lmap, load_json
 
@@ -249,6 +250,16 @@ def test_finetune(model):
         assert bart.decoder.embed_tokens == bart.shared
 
 
+def test_pack_dataset():
+    tokenizer = AutoTokenizer.from_pretrained("facebook/mbart-large-cc25")
+    tmp_dir = Path(make_test_data_dir())
+    save_dir = Path(tempfile.mkdtemp(prefix="packed_"))
+    pack_data_dir(tokenizer, tmp_dir, 128, save_dir)
+    orig_paths = {x.name for x in tmp_dir.iterdir()}
+    new_paths = {x.name for x in save_dir.iterdir()}
+    assert orig_paths == new_paths
+
+
 @pytest.mark.parametrize(
     ["tok"], [pytest.param(T5_TINY), pytest.param(BART_TINY), pytest.param(MBART_TINY), pytest.param(MARIAN_TINY)]
 )