Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

BlackRock 80/20 Target Allocation R (BRAPX Quick QuoteBRAPX - Free Report) has a 0.6% expense ratio and 0% management fee. BRAPX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. With yearly returns of 9.68% over the last five years, this fund clearly wins.

Janus Henderson Enterprise D (JANEX Quick QuoteJANEX - Free Report) is a stand out amongst its peers. JANEX is a Mid Cap Growth mutual fund. These funds aim to target companies with a market capitalization between $2 billion and $10 billion that are also expected to exhibit more extensive growth opportunities for investors than their peers. With five-year annualized performance of 11.42%, expense ratio of 0.79% and management fee of 0.64%, this diversified fund is an attractive buy with a strong history of performance.

American Funds Mutual Fund R6 (RMFGX Quick QuoteRMFGX - Free Report) : 0.27% expense ratio and 0.23% management fee. RMFGX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 10.18% over the last five years.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.