  Multimodal large language models (MLLMs) have gained significant attention
due to their strong multimodal understanding capability. However, existing
works rely heavily on modality-specific encoders, which usually differ in
architecture and are limited to common modalities. In this paper, we present
OneLLM, an MLLM that aligns eight modalities to language using a unified
framework. We achieve this through a unified multimodal encoder and a
progressive multimodal alignment pipeline. In detail, we first train an image
projection module to connect a vision encoder with LLM. Then, we build a
universal projection module (UPM) by mixing multiple image projection modules
and dynamic routing. Finally, we progressively align more modalities to LLM
with the UPM. To fully leverage the potential of OneLLM in following
instructions, we also curated a comprehensive multimodal instruction dataset,
including 2M items from image, audio, video, point cloud, depth/normal map, IMU
and fMRI brain activity. OneLLM is evaluated on 25 diverse benchmarks,
encompassing tasks such as multimodal captioning, question answering and
reasoning, where it delivers excellent performance. Code, data, model and
online demo are available at https://github.com/csuhan/OneLLM
