kaigi no saisyo ni, zikosyoukai wo simasita.

It means at the beginning of the meeting.

• 会議 = meeting
• の = links meeting to beginning, like of
• 最初 = beginning / first part
• に = marks the time point when something happened

So 会議の最初に is literally something like at the meeting’s beginning.

の connects two nouns.

Here, it shows that 最初 belongs to or is related to 会議:

• 会議 = meeting
• 最初 = beginning
• 会議の最初 = the beginning of the meeting

This is a very common pattern in Japanese:

• 学校の先生 = the school’s teacher / teacher at the school
• 本の名前 = the book’s title / title of the book
• 会議の最初 = the meeting’s beginning / beginning of the meeting

The に marks a specific time or occasion when the action happened.

In this sentence:

• 会議の最初に = at the beginning of the meeting
• 自己紹介をしました = did a self-introduction

So に tells you when the self-introduction happened.

This is similar to other time expressions:

• 3時に行きます = I will go at 3 o’clock.
• 朝に is less common in everyday speech, but 朝 can mark time too.
• 最初に話しました = I spoke first / at the beginning, I spoke.

Both 最初 and 始め can relate to the beginning, but they are not always used in exactly the same way.

In 会議の最初に, 最初 sounds very natural for the first part / the beginning of something.

• 最初 often emphasizes the first part or first in order
• 始め also means beginning, but it has a slightly different nuance and is used in other common expressions too

For this sentence, 会議の最初に is a normal, natural phrasing.

You may also see:

• 会議の始めに = at the start of the meeting

This is also possible, but 最初に is extremely common when talking about what happened first.

自己紹介 means self-introduction.

It is made from:

• 自己 = self
• 紹介 = introduction

So 自己紹介する means to introduce oneself.

Common examples:

• 自己紹介をします = I will give a self-introduction.
• まず、自己紹介をお願いします = First, please introduce yourself.

A native English speaker may want to say self introduction as two separate ideas, but in Japanese it is a fixed word: 自己紹介.

In Japanese, many actions are expressed as:

noun + をする

So instead of using a completely separate verb, Japanese often says:

• 自己紹介をする = to do a self-introduction

In past polite form, that becomes:

• 自己紹介をしました = did a self-introduction / introduced myself

This pattern is very common:

• 勉強をする = to study
• 質問をする = to ask a question
• 説明をする = to give an explanation

So 自己紹介をしました is a normal way to say I introduced myself.

Yes, in casual or natural conversation, を is often omitted with noun + する expressions.

So both are possible:

• 自己紹介をしました
• 自己紹介しました

Both mean the same thing here.

With を, the structure is a little more explicit and textbook-clear. Without を, it can sound a bit smoother in everyday speech.

Japanese usually puts the main verb at the end of the sentence.

So the structure is:

• 会議の最初に = at the beginning of the meeting
• 自己紹介を = self-introduction
• しました = did

This is a basic Japanese word order pattern:

time/place/etc. + object + verb

Examples:

• 昨日 映画を 見ました。 = I watched a movie yesterday.
• 教室で 日本語を 勉強します。 = I study Japanese in the classroom.

So in your sentence, the important action しました comes last.

しました is:

• past tense
• polite form

It comes from する = to do.

The forms are:

• する = plain non-past
• します = polite non-past
• した = plain past
• しました = polite past

So 自己紹介をしました means introduced myself or did a self-introduction, in a polite way.

Yes, the subject is omitted.

Japanese often leaves out the subject when it is clear from context. So this sentence does not explicitly say I, we, or they.

Depending on context, it could mean:

• I introduced myself at the beginning of the meeting
• We did self-introductions at the beginning of the meeting
• They did self-introductions at the beginning of the meeting

In many learning materials, it is often understood as I unless the context says otherwise.

Because the sentence is still complete without an explicit topic.

Japanese often omits は when the topic is already understood. If you wanted to make the topic explicit, you could say:

• 私は会議の最初に、自己紹介をしました。

That would mean:

• As for me, I introduced myself at the beginning of the meeting.

But if the speaker is already the obvious topic, Japanese usually leaves 私は out.

The comma is mainly there to make the sentence easier to read.

It separates the time phrase:

• 会議の最初に、

from the main action:

• 自己紹介をしました。

Japanese commas are often used more flexibly than English commas. This comma is helpful, but not absolutely required. You could also write:

• 会議の最初に自己紹介をしました。

That is still correct.

A simple reading is:

• 会議 → かいぎ
• 最初 → さいしょ
• 自己紹介 → じこしょうかい
• しました → しました

So the full sentence is:

かいぎ の さいしょ に、じこしょうかい を しました。

In natural pronunciation, it flows smoothly rather than word by word.

Normally, に is the natural choice here.

• に marks a point in time: at the beginning
• で usually marks the place where an action happens or the means by which it happens

So:

• 会議の最初に = correct and natural

Using で here would sound unnatural because 最初 is being treated as a time point, not really as a place.

By itself, the sentence does not clearly tell you.

• 自己紹介をしました can mean I introduced myself
• In some contexts, it can also refer to we did introductions or people introduced themselves

If you want to make it clearer, Japanese can specify:

• 私は自己紹介をしました。 = I introduced myself.
• みんなで自己紹介をしました。 = We all did self-introductions.
• 参加者は自己紹介をしました。 = The participants introduced themselves.

So the exact interpretation depends on context.